Nancy Lancaster (10 September 1897 – 19 August 1994) was a 20th-century tastemaker and the owner of Colefax & Fowler, an influential British decorating firm that codified what is known as the English country house look.

[2] At first the Trees took a 10-year repairing lease on Kelmarsh Hall near Market Harborough in Northamptonshire, which Nancy redecorated with help from Mrs Guy Bethell of Elden Ltd.

Tree was among a small group who saw the rising Nazi party in Germany as a threat to Britain, and he became a member of a clique of anti-appeasement MPs (who included Eden, Duff Cooper and others) who would meet at his house in Queen Anne's Gate.

However, this created additional difficulties on clear nights when a full moon was predicted - so the authorities looked for an alternative site north of London.

Nancy married, thirdly, in 1948, Lieutenant Colonel Claude Lancaster (1899–1977), a former military officer, country squire and member of Parliament who owned Kelmarsh Hall near Market Harborough, Northamptonshire.

Nancy Lancaster later claimed that it was the suffocating, day-to-day intimacy of marriage that made her realise why they were successful as lovers and ill-suited as husband and wife.

The renowned British interior designer David Hicks (1929–1998) called Nancy Lancaster "the most influential English gardener since Gertrude Jekyll."

Referred to as the doyenne of interior decorators (something she never was, nor ever claimed to be) and smart gardeners, she together with John Fowler created much of the English country house look.