Marion Barbara 'Joe' Carstairs (1 February 1900 – 18 December 1993)[1] was a wealthy British power boat racer known for her speed, eccentric lifestyle, and gender nonconformity.

[9] Her fourth and last husband, whom she married in 1920, was Serge Voronoff,[4] a Russian–French surgeon who become famous in the 1920s and 1930s for his practice of transplanting monkey testicle tissue into male humans for the claimed purpose of rejuvenation.

For some years Evelyn had believed in Voronoff's theories, and she funded his research and acted as his laboratory assistant at the Collège de France in Paris.

Openly lesbian, she had numerous affairs with women, including Dolly Wilde—Oscar Wilde's niece and a fellow ambulance driver from Dublin with whom she had lived in Paris—and a string of actresses, most notably Greta Garbo, Tallulah Bankhead and Marlene Dietrich.

Joe Carstairs married a childhood friend, the French aristocrat Count Jacques de Pret, on 7 January 1918 in Paris.

Carstairs (and her friends and lovers) lived in a flat above the garage,[16] which was situated near Cromwell Gardens in London's fashionable South Kensington district.

The cars and drivers could be hired for long-distance trips and the business specialised in taking grieving relatives for visits to war graves and former battlefields in France and Belgium.

[22] During this time, the North American press erroneously began referring to her as "Betty," a nickname she loathed; she claimed that journalists used it out of spite.

She paid $10,000 of her money to fund the building of one of the Blue Bird land speed record cars for Sir Malcolm Campbell, who once described her as "the greatest sportsman I know.

"[24] She was equally generous to John Cobb, whose record-breaking vehicle Railton Special was powered by the pair of engines from her powerboat Estelle V.[24] In 1934, Carstairs invested $40,000 purchasing the island of Whale Cay in the Bahamas where she lavishly hosted guests such as Marlene Dietrich and the Duke and Duchess of Windsor.