0:00:02 > 0:00:06In an idyllic Sussex landscape, created by master gardener Capability Brown,
0:00:06 > 0:00:12sits one of Britain's finest stately homes, Petworth House.
0:00:13 > 0:00:18Thanks to the National Trust, it's now open to us all.
0:00:18 > 0:00:23Except during winter when, like most of the Trust's homes, Petworth shuts the public out.
0:00:25 > 0:00:28When the house is closed, however, it's far from quiet.
0:00:32 > 0:00:37Normally, nobody gets to see what happens in here during the winter months. But this year,
0:00:37 > 0:00:41I've been given unique access to see what goes on behind the scenes.
0:00:41 > 0:00:47When the public have gone, the National Trust's expert conservation teams
0:00:47 > 0:00:51get the chance to do some housekeeping, on an epic scale.
0:00:51 > 0:00:56We get to see things up close that people don't see. It's amazing. Who else gets to do it?
0:00:57 > 0:01:02I had no idea until I took on this task quite how filthy the visitors were.
0:01:04 > 0:01:08And this winter, Petworth's got a new cleaner.
0:01:08 > 0:01:11- I can see that I've made a difference.- Have you waxed it?- No.
0:01:11 > 0:01:15It's a rare chance to get hands on with history...
0:01:15 > 0:01:17Ooh, it's heavy!
0:01:17 > 0:01:21..and glimpse the secret life of a great country house.
0:01:23 > 0:01:26On this visit, I'm set to work in Petworth's en-suite art gallery...
0:01:26 > 0:01:31take a turn round Britain's earliest globe...
0:01:31 > 0:01:35and reveal the hidden identity of a 2,000-year-old Roman.
0:01:37 > 0:01:41I'm joining perhaps the biggest spring clean in the world,
0:01:41 > 0:01:45which all takes place during the freezing months of winter.
0:02:01 > 0:02:05By January, Petworth House has been closed to the public for two months.
0:02:07 > 0:02:13But no matter how cold it gets outside, inside, conservation work carries on.
0:02:18 > 0:02:25Next on the winter schedule, the biggest and most time-consuming of all the rooms in the house.
0:02:25 > 0:02:29Several generations of the family who lived here were keen art collectors.
0:02:29 > 0:02:33So keen, in fact, they built their own gallery to house it all.
0:02:34 > 0:02:38It may look more like public institution than private home,
0:02:38 > 0:02:44but this sketch from the 1860s shows it could be playroom as well as museum.
0:02:46 > 0:02:51We all like to have a few pictures on the wall, but this takes it to a whole other level.
0:02:51 > 0:02:53Imagine growing up here. What a playground!
0:02:55 > 0:03:00Over the coming three weeks, however, the North Gallery will be our workplace.
0:03:00 > 0:03:03Petworth's six-strong housekeeping team will be joined by
0:03:03 > 0:03:07other conservation experts to carry out a range of tasks.
0:03:07 > 0:03:11Not just cleaning, but also scrutinising and investigating
0:03:11 > 0:03:15the National Trust's biggest single collection of art and sculpture.
0:03:15 > 0:03:24There's a dozen Turners in this room, as well as Gainsboroughs, and some rare works by William Blake.
0:03:24 > 0:03:29But the first artefact that needs our care is neither painting nor sculpture.
0:03:29 > 0:03:33House steward Susan Rhodes is about to reveal it to me.
0:03:33 > 0:03:37The shutters are drawn and there's still another cover over this object
0:03:37 > 0:03:40so it must be something that's really light sensitive.
0:03:40 > 0:03:43- It is, yes.- It's like the mystery object.- Yes.- What's inside?
0:03:43 > 0:03:49- This is a fantastic, very early, rare English globe.- Wow.
0:03:49 > 0:03:50How early is early?
0:03:50 > 0:03:531592. It's the earliest English globe in existence.
0:03:55 > 0:03:59This plastic cover comes off just once a year,
0:03:59 > 0:04:03so the team can perform a close up check of the object's condition.
0:04:03 > 0:04:07The globe came to Petworth thanks to the ninth Earl of Northumberland.
0:04:07 > 0:04:11His love of learning earned him the nickname "the Wizard Earl".
0:04:11 > 0:04:15According to family lore, he was given the globe by Sir Walter Raleigh
0:04:15 > 0:04:18while both men were imprisoned in the Tower of London.
0:04:22 > 0:04:26It's a rare object which the conservation team don't dust.
0:04:26 > 0:04:31Made largely from paper, it's too fragile for even the lightest of brushes.
0:04:31 > 0:04:34We still need to inspect it for damage, however.
0:04:34 > 0:04:38We'll look all over globe and look for anything that looks fresh.
0:04:38 > 0:04:44These big patches where things are missing are obviously old because they're discoloured and blend in.
0:04:44 > 0:04:50Unfortunately, a lot of people have gone, "Here we are," and rubbed the UK away.
0:04:50 > 0:04:53You can just see the west coast and you can see Ireland.
0:04:53 > 0:04:56Of course, it's incredibly attractive for pests.
0:04:56 > 0:05:02- It's been riddled in the past. Not the globe itself.- Not the globe itself, but the stand is.
0:05:02 > 0:05:07- Pests like to eat paper, don't they? - They do, things like silverfish graze across it like cows.
0:05:07 > 0:05:12Oh, I love this, have you seen on this side? Is that a sea monster?
0:05:12 > 0:05:15Yeah, it's got different sea monsters in different areas.
0:05:15 > 0:05:17Gosh, what a wonderful thing.
0:05:17 > 0:05:21What is it makes this object so light sensitive?
0:05:21 > 0:05:25It is the fact that it's paper, and you could lose that surface detail.
0:05:25 > 0:05:29So in a sense, it's a huge, round drawing.
0:05:29 > 0:05:33- Exactly, and it's just as fragile. - And they have to be kept in the dark otherwise they fade.
0:05:33 > 0:05:40For this inspection, we're briefly shining a working lamp on the object.
0:05:40 > 0:05:42However, even the dimmest of ambient daylight can still cause
0:05:42 > 0:05:50a photochemical reaction in paper, producing acids which attack its fibres, and fading coloured dyes.
0:05:50 > 0:05:56The whole spectrum of light can cause damage, including ultraviolet.
0:05:56 > 0:06:00- UV is the most dangerous type of light.- I knew it was for skin, but I didn't know it was for objects.
0:06:00 > 0:06:04Our skin is basically organic material. It's the same as paper.
0:06:04 > 0:06:09All the windows in National Trust houses have a UV film on which you can't see.
0:06:09 > 0:06:15It doesn't stop you from looking out, but just dramatically reduces the amount of UV that's allowed in.
0:06:15 > 0:06:21But since any light causes some decay, the team must continually monitor levels.
0:06:21 > 0:06:27With this, we can measure the amount of lux, which is what we measure light in, that's hitting the globe.
0:06:27 > 0:06:29On an open day we would aim to keep it below 50.
0:06:29 > 0:06:33Obviously our conservation lights, which are essential for the visual inspection...
0:06:33 > 0:06:36You can't inspect it if you can't see it.
0:06:36 > 0:06:40..dramatically increase the light. That is three times the light levels we keep it at.
0:06:40 > 0:06:45The Trust also uses another less hi-tech tool.
0:06:45 > 0:06:50This sits on the edge of the case on the globe all the time, so when it's uncovered, this is uncovered.
0:06:50 > 0:06:56- This is a blue wool dosimeter.- A blue what-ometer?- A blue wool dosimeter.
0:06:56 > 0:07:01This is a British standard blue wool which fades at a known rate.
0:07:01 > 0:07:05So we leave it on there for the season, and then it's sent away to our conservators
0:07:05 > 0:07:08who can then tell us how much light the object's had.
0:07:08 > 0:07:14If we open it up you can just see the change in colour.
0:07:14 > 0:07:16- That's quite striking, isn't it? - It is. It's really different.
0:07:16 > 0:07:20- That's a year's worth of fade, is it?- That's a season's worth.
0:07:20 > 0:07:25March to the beginning of November. It shows you why it's so important to monitor your light levels.
0:07:25 > 0:07:32If we were open 365 days a year and ten-hour days, a lot of these objects wouldn't last as long as they will
0:07:32 > 0:07:35with the restrictive opening times.
0:07:42 > 0:07:47The statues we're working on have been housed here since the 1750s.
0:07:47 > 0:07:51They are the reason the North Gallery was first created.
0:07:51 > 0:07:55They were brought to Petworth by Charles Wyndham,
0:07:55 > 0:07:59the second Earl of Egremont, a leading politician of his day.
0:07:59 > 0:08:04Like every self-respecting English milord of the 18th century, the Earl had been on the Grand Tour
0:08:04 > 0:08:09where he acquired a taste for all things Italian, all things classical.
0:08:09 > 0:08:13And he pillaged half of Italy for his extraordinary collection.
0:08:14 > 0:08:18When the second Earl bought these survivors from ancient Greece and Rome,
0:08:18 > 0:08:25they were already up to 2,500 years old, and many were missing limbs, noses, even heads.
0:08:28 > 0:08:32Taking the opposite approach to today's National Trust,
0:08:32 > 0:08:37the statues were repaired by skilled sculptors in Italy or England.
0:08:37 > 0:08:44For years, objects like this were turning up almost every month in crates here in West Sussex.
0:08:44 > 0:08:49So many classical sculptures did he buy that art history is still only catching up
0:08:49 > 0:08:53with the real story about a lot of the objects in Petworth's collection.
0:08:55 > 0:08:58In the corner of the Little Dining Room, for instance,
0:08:58 > 0:09:01is one which doesn't even rate a mention in the guidebook.
0:09:01 > 0:09:06It's referred to merely as "young man in toga".
0:09:06 > 0:09:10But there's an archaeologist who reckons this may be someone much more important.
0:09:10 > 0:09:15A notorious figure from Roman history who's been hiding out in West Sussex.
0:09:15 > 0:09:18In an attempt to uncover the sculpture's hidden identity,
0:09:18 > 0:09:23Dr Miles Russell has come to analyse it in-depth.
0:09:23 > 0:09:25- So here you go.- Oh, fantastic.- This is what you were after.
0:09:25 > 0:09:30He's a little smaller than I expected,
0:09:30 > 0:09:32but it's certainly mid-first century AD.
0:09:32 > 0:09:38And that's the kind of pose, as well, of the young man, almost like a magistrate.
0:09:38 > 0:09:42He's got official documents there, and he's standing in a pose waiting to speak to the Empire.
0:09:42 > 0:09:49Miles has been searching for images of none other than the Emperor Nero when he was a teenager.
0:09:49 > 0:09:53Such statues are extremely rare because Nero grew into such
0:09:53 > 0:09:58a monstrous tyrant, nobody wanted to keep a marble souvenir of him.
0:09:58 > 0:10:02There's a lot of damage to the neck. All the images we've seen of Nero
0:10:02 > 0:10:05have been smashed after his death
0:10:05 > 0:10:10as an attempt to eradicate him completely out of Roman history.
0:10:10 > 0:10:14Or, there is a tendency in the 18th century to add bits, to reconstruct,
0:10:14 > 0:10:17and that's something the scan will certainly pick out.
0:10:21 > 0:10:23To reveal the truth about this statue,
0:10:23 > 0:10:30the archaeologists have brought with them some technology more commonly used by the police in forensic work.
0:10:30 > 0:10:32The face is the most important thing.
0:10:32 > 0:10:35If you can get some nice clean images of that.
0:10:35 > 0:10:40The laser scan builds up an extremely detailed 3D model,
0:10:40 > 0:10:47every part of which can be compared with the only two statues of the teenage Nero which have survived,
0:10:47 > 0:10:48one in Parma, the other in Paris.
0:10:50 > 0:10:52Oh, that's fantastic, isn't it? That is brilliant.
0:10:52 > 0:10:54You can see the eyes extremely clearly.
0:10:54 > 0:11:00- That pouty mouth, and the chin, that is brilliant.- His eyes have come up really nicely.
0:11:00 > 0:11:05That chin, and the position of those lips, that's classic Nero.
0:11:06 > 0:11:09That's him, isn't it?
0:11:09 > 0:11:14The scan is of keen interest to house manager Andrew Loukes.
0:11:14 > 0:11:19- How's it going?- It's coming up brilliantly, actually, as you can see.- So do we think it's him?
0:11:19 > 0:11:21I think it almost certainly is.
0:11:21 > 0:11:24It is early-to-mid 1st century AD.
0:11:24 > 0:11:29The fact that it's made out of marble would suggest an important member of the imperial household.
0:11:29 > 0:11:33The fact that it's a boy suggests it's a person about to achieve great things,
0:11:33 > 0:11:37so all these things narrow it down until there's really only one candidate left.
0:11:37 > 0:11:43What can you really tell by the scan that we couldn't really see with the naked eye?
0:11:43 > 0:11:48The problem with looking with the naked eye is the way that shadow goes, the way that lighting goes,
0:11:48 > 0:11:53whereas here, in the scan, you've done away with all the artificial lighting conditions,
0:11:53 > 0:11:58- and you can see the eyes, you can see the crisp shape of the eyelids extremely clearly.- Oh, you can.
0:11:58 > 0:12:03- You can turn it from all directions. You can see the beginnings of a double chin there.- Oh, yeah.
0:12:03 > 0:12:07- Got into bad habits early, did he? - Well, he did, yes, all that sort of imperial food in the palace.
0:12:07 > 0:12:13- This is one of three complete young Neros.- So it's incredibly rare.
0:12:13 > 0:12:15- Yes, oh, yes, very much so, and incredibly important.- Yeah.
0:12:15 > 0:12:17- Congratulations.- Thank you.
0:12:17 > 0:12:20- We've won the lottery.- Indeed.
0:12:20 > 0:12:27It's a discovery of international significance, yet it's been hiding in plain sight for centuries.
0:12:27 > 0:12:33This previously ignored statue can now be counted as one of Petworth's most important treasures.
0:12:37 > 0:12:43The man who brought all these antique statues to Sussex, the second Earl of Egremont,
0:12:43 > 0:12:50died suddenly in 1763, according to family legend, after one turtle dinner too many.
0:12:52 > 0:12:57His son, the third Earl, presided over what's seen as Petworth's Golden Age.
0:12:59 > 0:13:05In the 1820s, he extended the North Gallery to its present immense size.
0:13:05 > 0:13:10He was collecting even more sculpture, though of a different kind to his father.
0:13:10 > 0:13:14The third Earl laid down a challenge to the British sculptors of his day.
0:13:14 > 0:13:18For years, they had complained there were no enlightened patrons.
0:13:18 > 0:13:21Aristocrats only wanted portraits of themselves.
0:13:21 > 0:13:27They had no chance to flex their muscles, to compete with the great Michelangelo.
0:13:27 > 0:13:31So the third Earl said, "OK, if you think you can do it, carve me
0:13:31 > 0:13:35"some monumental, classically inspired sculptures."
0:13:38 > 0:13:42This is how John Flaxman rose to the challenge.
0:13:46 > 0:13:51Begun in 1817, completed nine years later,
0:13:51 > 0:13:55St Michael Overcoming Satan is over 11 foot tall.
0:14:02 > 0:14:05Now it's the next thing I am supposed to be conserving.
0:14:07 > 0:14:08I'm looking forward to this.
0:14:12 > 0:14:14I think that this is, um...
0:14:16 > 0:14:21..maybe the finest 19th-century British sculpture.
0:14:21 > 0:14:23Certainly one of them. It's an absolutely...
0:14:26 > 0:14:29How do you do, Archangel Michael?
0:14:29 > 0:14:35What a great treat to see it from up here, from Archangel Michael's perspective,
0:14:35 > 0:14:37staring down at Satan.
0:14:37 > 0:14:43From up here, it looks as though Satan is about to plunge down into the abyss from the height of heaven.
0:14:43 > 0:14:48The best thing of all is the way in which that foot of the archangel
0:14:48 > 0:14:51goes underneath the arm of Satan,
0:14:51 > 0:14:58and you can get this fantastic contrast between the smoothness of Michael's leg
0:14:58 > 0:15:03and Satan's thick, heavy, veined forearms.
0:15:03 > 0:15:06You can see that Satan has got blood coursing through his veins,
0:15:06 > 0:15:11and that's such a difficult skill, to carve the veins proud like that.
0:15:11 > 0:15:15The whole piece is carved from a single block
0:15:15 > 0:15:19and it's an absolutely phenomenal, phenomenal achievement.
0:15:20 > 0:15:23But of course, I didn't climb up here to rhapsodise.
0:15:23 > 0:15:28I'm supposed to be cleaning. Even after half a winter, however...
0:15:28 > 0:15:33there are aspects of conservation work I still find challenging.
0:15:35 > 0:15:42There's no way putting on one of these hoovers with anything even resembling elegance if you're me.
0:15:47 > 0:15:51It's actually covered in dust.
0:15:51 > 0:15:54Petworth's statues are dry-clean only.
0:15:54 > 0:16:00Washing could both remove the original colour and texture of the surface or stain the porous stone.
0:16:03 > 0:16:08I am sorry about this, but I've been told to clean all of you.
0:16:08 > 0:16:11It seems most indecent and very personal.
0:16:11 > 0:16:14Oooh! I hope you're not ticklish.
0:16:14 > 0:16:18This is the reality of working at Petworth.
0:16:18 > 0:16:21The profane side by side with the sacred.
0:16:21 > 0:16:27Such distinctions become irrelevant in the face of a greater, more permanent truth - dust.
0:16:41 > 0:16:45Outside, temperatures are stuck below zero.
0:16:45 > 0:16:48Inside, it doesn't feel much better.
0:16:48 > 0:16:54Although Petworth House had heating installed in the 20th century, it's hardly ever switched on.
0:16:54 > 0:16:58Why do we have to freeze? It's so cold in here.
0:16:58 > 0:17:02It's not too bad. I mean, I have to be honest, I am wearing three layers,
0:17:02 > 0:17:08- a gilet and thermals.- You look like you've just stepped out of a chalet!
0:17:08 > 0:17:12This is one of the main reasons we don't open to the public.
0:17:12 > 0:17:14- It becomes unvisitable.- Yes.
0:17:15 > 0:17:21Visitors often assume it's uneconomic to warm a house on this scale in winter,
0:17:21 > 0:17:27but cost is not the main reason why most historic homes have to be careful about heating.
0:17:27 > 0:17:31The problem with heating a room too much is that it starts to dry out
0:17:31 > 0:17:38and a very dry room means that paintings, their frames and their canvasses will start to crack.
0:17:38 > 0:17:42What we're more concerned with here is relative humidity,
0:17:42 > 0:17:46not temperature. That's how moist or how dry the atmosphere is.
0:17:46 > 0:17:50Too damp an environment would also be a problem.
0:17:50 > 0:17:55Wood can swell, metals corrode, and mould and insects become more likely.
0:17:55 > 0:17:59So humidity levels throughout the house need to be controlled.
0:17:59 > 0:18:02We have a band of 50% to 65%.
0:18:02 > 0:18:08That's the amount of moisture that we like to keep in the objects so they are at a stable condition.
0:18:08 > 0:18:11In the summer, do you turn have air conditioning to make it cooler?
0:18:11 > 0:18:15In the summer when it's warm, the heating often comes on...
0:18:15 > 0:18:22- Great(!)- It's quite humid in the summer and so the way of taking that moisture away is to dry...
0:18:22 > 0:18:25Oh, you disperse? Oh, I see.
0:18:25 > 0:18:31- We boil in the summer and freeze in the winter - all in the name of art? - Exactly, all in the name of art.
0:18:40 > 0:18:44The masterpieces of Petworth aren't just made of stone and canvas, of course.
0:18:44 > 0:18:51Some of the furniture here can definitely be counted as art in its own right.
0:18:51 > 0:18:55Sue and I are about to clean a commode from 1710,
0:18:55 > 0:18:59when that word meant low cabinet rather than toilet.
0:19:00 > 0:19:04It's in a style found throughout Petworth. Boulle work.
0:19:04 > 0:19:09What's special about this item is that Andre Charles Boulle himself built it.
0:19:09 > 0:19:15- This is my favourite thing in the collection. I think it's beautiful. - This is your favourite piece?
0:19:15 > 0:19:19- My favourite out of the whole house. It's just a stunning piece.- Wow.
0:19:19 > 0:19:21It's tortoiseshell inlaid with brass.
0:19:21 > 0:19:23The brass is dulled down over time,
0:19:23 > 0:19:27but it would have been a shocking contrast against the dark of the tortoiseshell.
0:19:27 > 0:19:30- And is it possible now to bring it back?- It would be possible, yeah.
0:19:30 > 0:19:36It's just the tarnish and dirt that's built up over the brass, but, this is part of this piece's history now,
0:19:36 > 0:19:41and the Trust has a policy of consolidating condition rather than restoring to new.
0:19:41 > 0:19:45Gosh. I must say, in the case of something like this, I wouldn't agree with that
0:19:45 > 0:19:48because the aesthetic affect of the object has been compromised.
0:19:48 > 0:19:52It's one of those ongoing arguments with the Trust and the general heritage industry.
0:19:52 > 0:19:58You have to think that this piece is part of an interior scheme, and you have to think of the tonality.
0:19:58 > 0:20:03If you restore this to new-looking, it would then offset against the Turner frame above it,
0:20:03 > 0:20:07- which would then offset against the walls.- Nah, I don't agree.
0:20:07 > 0:20:14'Unmoved by my opinion, Sue gets on with the cleaning she is allowed to do.'
0:20:14 > 0:20:18I'm going to start here on these fantastic ormolu sphinxes heads.
0:20:18 > 0:20:20- She's a sphinx?- She is.
0:20:20 > 0:20:23Andre Charles Boulle is clearly flattering Louis XIV
0:20:23 > 0:20:26by comparing them to these mystical creatures of wisdom and knowledge.
0:20:26 > 0:20:30And these deposits in here, that I can see?
0:20:30 > 0:20:34Again, this is where dust has built up over time. We won't get this off.
0:20:34 > 0:20:37This isn't coming off with a brush. Once it kind of gets to this point
0:20:37 > 0:20:42where it's proper ingrained, this is historic dust, so it's almost...
0:20:42 > 0:20:45- Historic dust!- Historic dust!
0:20:45 > 0:20:49One of the amazing things about the construction of this piece is it's so well made
0:20:49 > 0:20:54that it is airtight inside and has its own kind of micro-climate within the piece,
0:20:54 > 0:20:58which causes us problems because it gets too humid in there, too damp,
0:20:58 > 0:21:04and we get mould growth inside and on the drawers - which you can see - and we're going to take that off now.
0:21:04 > 0:21:11'Clearly this is one of part of the object's history that the Trust doesn't feel the need to preserve.
0:21:11 > 0:21:15'To keep mould at bay, the team generally leaves the commode's drawers open
0:21:15 > 0:21:17'when visitors aren't around.
0:21:17 > 0:21:19'That way, they're kept ventilated.
0:21:22 > 0:21:29'The marble top is cleaned with the usual mix of water and sensitive skin washing-up liquid.
0:21:29 > 0:21:32'Once rinsed and dried, it's coated with wax.
0:21:32 > 0:21:36'Unlike the beeswax used on wood, or the paraffin wax used on floors,
0:21:36 > 0:21:44'this is a petroleum-based microcrystalline variety, which makes it both finer and denser.'
0:21:44 > 0:21:50We wax the surface of the marble tops because it gives it a protective layer during a busy open season.
0:21:50 > 0:21:54Most people might be quite surprised to learn that marble's actually incredibly porous.
0:21:54 > 0:22:00This just stops the dirt and dust that's going to fall on it from getting ingrained in the surface.
0:22:00 > 0:22:06I like these rather gormless Turner sailors, looking at you. "What's she doing down there?"
0:22:06 > 0:22:12So many of our visitors are so busy staring at the Turner that they forget the furniture underneath it.
0:22:14 > 0:22:18The rest of the team have been busy checking and dusting
0:22:18 > 0:22:21the North Gallery's 107 paintings and frames,
0:22:21 > 0:22:26which isn't the easiest of tasks if they are hung 20 feet high.
0:22:28 > 0:22:34Sometimes outside specialists join them to carry out more in-depth conservation.
0:22:34 > 0:22:39Sophie Reddington's come to care for one of Petworth's Gainsboroughs.
0:22:39 > 0:22:41During my painting survey a couple of years ago,
0:22:41 > 0:22:44I established this painting hadn't been touched
0:22:44 > 0:22:46for a very, very long time - decades.
0:22:46 > 0:22:50- So it's a general 25 years' service? - It is, exactly.
0:22:56 > 0:23:03Oh, I can see some lifting paint here, all along the bottom edge.
0:23:03 > 0:23:06- Oh, yes.- We'll have to do something about that.
0:23:06 > 0:23:10The flaking was probably caused by changes in humidity
0:23:10 > 0:23:14in the days when the gallery used to have the central heating on.
0:23:14 > 0:23:19The first stage of treatment is to glue the flaking paint back down.
0:23:19 > 0:23:21It's a very liquid glue with a low viscosity
0:23:21 > 0:23:25which means that it sinks into the layers quite easily.
0:23:25 > 0:23:28It can flow nicely
0:23:28 > 0:23:29into the cracks.
0:23:29 > 0:23:36I'm rolling a cotton wool swab, which I moisten with a little of my saliva,
0:23:36 > 0:23:41to remove the excess glue from the paint surface.
0:23:41 > 0:23:47Now I'm taking a piece of Bondina, which is a sort of non-stick paper,
0:23:47 > 0:23:53and I'm trying to iron the paint to flatten it again.
0:23:53 > 0:23:55The paper reduces the risk of the paint being damaged.
0:23:57 > 0:23:59This is a specially developed heating spatula.
0:23:59 > 0:24:03I can still easily touch it with my hand.
0:24:03 > 0:24:07It's really just to introduce a little bit of warmth
0:24:07 > 0:24:11to help the glue flow better between the layers.
0:24:11 > 0:24:17Many decades ago, this process was actually carried out with ordinary kitchen irons.
0:24:17 > 0:24:19It sounds very housewifey!
0:24:23 > 0:24:25I don't really like ironing, to be honest.
0:24:25 > 0:24:29I'm leaving it under weights for a while
0:24:29 > 0:24:32because the glue is not quite dry yet,
0:24:32 > 0:24:35and I'm moving onto the next section.
0:24:35 > 0:24:40What Sophie's doing here is another example of the National Trust's
0:24:40 > 0:24:47preference for conservation rather than restoration. She's not trying to make the painting look brand new.
0:24:47 > 0:24:52Instead, just like the Petworth regulars, her goal is to preserve current condition.
0:24:52 > 0:24:59That requires her to pay more attention to the frame than most visitors probably give the picture.
0:24:59 > 0:25:06She has to clean places no-one else ever sees, because dust can attract insects or mould wherever it lurks.
0:25:06 > 0:25:11The back needs some minor repairs, so Sophie calls upon another of her many skills...
0:25:11 > 0:25:14carpentry.
0:25:16 > 0:25:21The main thing to avoid is just really drilling through the canvas.
0:25:21 > 0:25:24That would be an absolute awful thing to happen.
0:25:24 > 0:25:27That's why I have chosen a very thick piece of board
0:25:27 > 0:25:30to make sure I'm safe.
0:25:32 > 0:25:36Then it's time to give the surface of the painting a clean.
0:25:36 > 0:25:40The house team only get to dust, but Sophie is allowed to wash.
0:25:40 > 0:25:45The amount of water I'm introducing onto the paint surface
0:25:45 > 0:25:48is actually very minimal,
0:25:48 > 0:25:53because if I were to use too much water,
0:25:53 > 0:25:57then I could actually affect the surface in a really bad way.
0:25:57 > 0:26:02The varnish might blanch, crack into really sort of fine, hairline cracks.
0:26:02 > 0:26:10What little water Sophie does apply has had any corrosive mineral content removed by de-ionisation.
0:26:11 > 0:26:14This dirt is surface dust.
0:26:14 > 0:26:20In this case, plain de-ionised water seems to do the trick.
0:26:20 > 0:26:26But sometimes you need far stronger cleaning agents to be able to remove old dust and dirt.
0:26:32 > 0:26:39This is a very personal, romantic landscape by Gainsborough from the mid-1770s.
0:26:39 > 0:26:44It was much admired by another of the artists who stayed at Petworth during the third Earl's era.
0:26:44 > 0:26:45None other than John Constable.
0:26:48 > 0:26:50- It's done. I finished it. - It looks a lot cleaner.
0:26:50 > 0:26:54I really feel like it has cheered up a bit.
0:26:54 > 0:26:59Those swabs really indicate how much dirt there was on the painting.
0:26:59 > 0:27:03- There's more colour in it, it's just generally lifted.- Yes.- Terrific.
0:27:06 > 0:27:10Service and MOT complete, Gainsborough's put back
0:27:10 > 0:27:15on Petworth's walls, where he's hung for nearly 250 years.
0:27:19 > 0:27:24After three freezing weeks, work in the North Gallery is complete.
0:27:26 > 0:27:29They may now look like ghosts, but I've learned
0:27:29 > 0:27:34that all of these statues are, in a sense, very much alive.
0:27:34 > 0:27:39Every one has its own story of how it came to be here and how it needs to be cared for.
0:27:39 > 0:27:43And one statue above all really sums that up.
0:27:44 > 0:27:47I do think it's an extraordinary story.
0:27:47 > 0:27:52I mean, this is really Petworth House's Antiques Roadshow moment.
0:27:52 > 0:27:58This rather overlooked sculpture in the corner of the room, object number 55, boy with a toga,
0:27:58 > 0:28:06suddenly turns out to be one of the most precious, one of the most rare objects in the whole collection.
0:28:06 > 0:28:08From zero to Nero.
0:28:08 > 0:28:14It's a measure of just how incredibly rich the collections at Petworth House are,
0:28:14 > 0:28:17that they can contain a revelation like this.
0:28:17 > 0:28:24And it makes you wonder how many other surprises may lurk elsewhere in the house.
0:28:24 > 0:28:26Goodnight, Master Nero.
0:28:33 > 0:28:36Subtitles by Red Bee Media Ltd