On the death of Col. Turnour in 1930 and in accordance with Lady Fetherstonhaugh's wishes, Uppark passed to Admiral The Hon. Sir Herbert Meade, 4th Earl of Clanwilliam.
He and his wife Margaret, having visited Col. Turnour several times at Uppark, returned once more on 11 February 1931 "to enter into the fairy story of our lives at Uppark."
The new Lady Meade-Fetherstonhaugh threw herself into her new role, one of restoring Uppark to its former glory. The roof was repaired, paintwork renewed, and she embarked on an eight year period of textile conservation, during which many new techniques were developed in conjunction with the Royal School of Needlework.
The fragile yet filthy window and bed curtains were cleaned "by being pulled over dewy grass" or by immersion in water infused with the herb soapwort (also known as Wild Sweet William, Saponaria officinalis).
Silk that had become fluffy had the material lain flat by couching thread sewn in parallel lines. The hangings of the Prince Regent's bed were repaired in 1931-32 by, in some areas, as many as 20 rows of stitching to one inch.
From 1931 to 1934 furniture was fumigated and repaired, china washed, chandeliers cleaned and secured, and the amassed paperwork of deeds and manuscripts aired and sorted. By 1939, Lady Meade-Fetherstonhaugh surmised that she and her staff had "mended and re-hung twenty-eight brocade curtains, three Queen Anne four-poster beds, and a set of chairs."
As a result of this pioneering work, she rapidly made a name for herself as something of an expert on the subject. She was soon asked to repair textiles from other properties such as The Vyne in Hampshire, Syon House in Middlesex, and even from abroad across Europe and America where, despite being in her eighties, she later conducted a "hectic six week lecture tour."
With the war over, Admiral Meade-Fetherstonhaugh and his son Richard approached the National Trust with an offer to protect Uppark for the future. Negotiations were complex and protracted, but eventually an endowment was put together of grants, standing timber on the estate, and a substantial sum from an anonymous lady who had never seen the house, but was inspired by a description given over the telephone by a member of the National Trust. As a result, Uppark passed to the trust in 1954.
In 1958 Lady Meade-Fetherstonhaugh's son Richard died, followed by her husband in 1964. The following year she relinquished her tenancy of Uppark to her widowed daughter-in-law.
On her death in 1977, the 11th Duke of Argyll described Lady Meade-Fetherstonhaugh as "the visionary behind... the complete reinstatement of the building to its former glory," surmising that together with her husband they had "dedicated their lives at very great personal sacrifice to bringing back its furnishings and fabrics to their original 18th century condition for the world to enjoy after them."