The restoration is the largest project of its kind taken on by the trust and will have cost pounds 20m by the time it is finished. Forgotten skills, such as the modelling of rococo plasterwork, have been rediscovered in the course of the work, which has been undertaken by hundreds of craftsmen.
In its determination to restore the house to its state the day before the fire, the trust has pioneered new extremes of historical correctness. Gilt decoration has been painstakingly burnished and then distressed with an overcoat of artificial dirt designed to resemble two or three centuries of grime. Wallpapers have been reprinted in a dozen or more shades to reproduce the exact colouring of rooms before the fire.
A flock wallpaper in the red drawing room, which was a bright crimson in 1851, has been restored to resemble its faded 1991 colours. The wallpaper now varies in colour from cafe au lait, where it is fully bleached by the sun, back to deep crimson where it has been protected by pictures. The large crimson patches were fully evident yesterday, but when the pictures are returned the patches will be mostly covered.
Rooms throughout Uppark have been redecorated to preserve the ageing effects of sunlight - rooms that were originally a bright white, produced by white lead paint, faded to silver grey, and cool cream colours turned a light buff. They have been restored to the same subdued shades so that faded furnishings, which were mostly saved from the fire, will not look out of place when returned.
Nigel Seeley, surveyor of conservation for the trust, said: 'We have not gone in for any theatrical distressing of the furnishings. We haven't knocked pieces of plaster off where they had been knocked off before the fire.'
Uppark was built in 1690 but was extensively remodelled by Sir Harry Fetherstonhaugh with the architect Humphry Repton between 1810 and 1815. Sir Harry wooed Emma Hart, a London night club hostess, who later, as Emma Hamilton, became Nelson's mistress. When Sir Harry lost Emma and fell out of favour with the Prince of Wales he poured his energy into remodelling Uppark.
Sir Harry used Repton to redesign the dining room and the adjacent servery, installing a stained- glass window with classical figures in formal poses. Sitting at table in the rococo dining room, Sir Harry Fetherstonhaugh could look past gilt mirrors and through the doorway of the servery to admire the stained glass lit from behind by lamps at night.
When Uppark opens the public will be able to see the print room for the first time. It was formerly part of the family's private quarters. As prints became popular in the 18th century it became fashionable for the rich to paste them up in special rooms. So engravings of Old Flemish and Italian masterworks decorate the room, a miniature art gallery filtered through 18th-century eyes.