Arthur Ronald Lambert Field Tree (26 September 1897 – 14 July 1976) was a British Conservative Party politician, journalist and investor who served as the Member of Parliament (MP) for the Harborough constituency in Leicestershire from 1933 to 1945.

There he was tutored by a convent girl from Cork in Ireland, his governess Kate Walsh, who was also Arthur's partner, the mother of six further half-siblings of Ronald; Dennis (1898–1969), Kathleen (1901–1975), Patrick (1905–1991), James, Gerald and Elizabeth Waring (1914–1991).

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

[7] On the outbreak of war, the security forces were concerned by the visibility of Churchill's country house Chartwell, its high topographical location and the fact it was south of London making it an easy target for German bombers returning from raids on the capital.

[6] Churchill gave Tree a job in the Ministry of Information, where he met a married American co-worker Marietta Peabody FitzGerald and began a romantic relationship.

[4] Marietta had started an affair with Adlai Stevenson between his two failed presidential campaigns, but her husband was unfazed by this, as the couple's marriage had largely disintegrated to a friendly separation, with Tree spending much of his time at Heron Bay, his house in Barbados.

Marietta had turned down the option of returning to her earlier lover, the director John Huston, even when he had given her a role in his 1960 movie The Misfits.

In his childhood, Ronald would have known both the Tree family house at 94 Cass Street, (now Wabash but since demolished) built to a design by the eminent Henry Hobson Richardson, one of the greatest of American architects in the latter half of the 19th C. and the Tree Studio Building and Annexes, a surviving example of the work of Parfitt Brothers architects and now on the U.S. National Register of Historic Places.

Arthur and Ronald also lived for a time at a (now Grade II*) London house in Harrington Gardens designed by the significant Victorian architects of Sir Ernest George and Peto.

Following his father and grandfather, Ronald was the owner at various times of two of England's finest historic country houses, Ditchley Park and Kelmarsh Hall.

With a foot in England and one across the Atlantic, it is not surprising that he enjoyed the warmer climes and relaxed colonial ambience of Barbados - not least escaping post-War austerity - where he founded and built the Sandy Lane resort and hotel towards the end of his life.