Count Jacques de Pret, on 7 January 1918 in Paris. The purpose of the marriage was simply to allow Carstairs’ access to her trust fund independently of her mother. The marriage was annulled immediately after her mother's death on the grounds of non-consummation. By means of a deed poll, she renounced her married name and resumed using the name Carstairs in February 1922. In 1920, with three former colleagues from the Women's Legion Mechanical Transport Section, she started the X-Garage, a car-hire and chauffeuring service that featured a women-only staff of drivers and mechanics. Carstairs (and her friends and lovers) lived in a flat above the garage, which was situated near Cromwell Gardens in London's fashionable South Kensington district. Several of the X-Garage staff had served as drivers during the war and spoke French, German, or Italian. 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. They were also hired for journeys within London and the garage had an arrangement with the Savoy Hotel to transport guests to the theatre or to shows. During the early-1920s, X-Garage cars were a familiar sight in London's fashionable circles. In 1925, X-Garage closed and Carstairs inherited a fortune from Standard Oil via her mother and grandmother. The same year, she had her first speedboat built and named it Gwen after one of her former lovers, Gwen Farrar. But it was soon renamed Newg after capsizing on a test run. With it, she won her first trophy, the Southampton Water trophy. She was also given a Steiff doll by a girlfriend, Ruth Baldwin (1905 – August, 1937), naming it Lord Tod Wadley. She became exceptionally attached to this doll, keeping it with her until her death, although—unlike Donald Campbell's mascot 'Mr Whoppit'—she didn't take it into her speedboats for fear of losing it. She had clothes made for it in Savile Row and had its name placed with her own on the name plaque on the door of her London apartment. Between 1925 and 1930, Carstairs spent considerable time in powerboats and became a very successful racer winning many notable trophies – the Duke of York's Trophy in 1926, the Royal Motor Yacht Club International Race, the Daily Telegraph Cup, the Bestise Cup, and the Lucina cup. Still, the Harmsworth Trophy she longed for