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."