The steel screw schooner Mairi was designed for the Marquis of Graham by William Beardmore & Co. of Dalmuir, near Glasgow. Built on the Clyde at Whiteinch by Ritchie, Graham & Milne in 1911, she was registered at 59 tons gross (35 net and 65 Thames) and measured 80 feet in length with a 14 foot beam. Initially hired and subsequently purchased by the Admiralty early in the Great War, she was fitted with a 3-pounder gun and was mostly employed as a submarine depot ship although one record states she was used latterly as a tug (after March 1918). Sold back into private ownership in August 1919, she was purchased by the eminent lawyer, the 1st Lord Birkenhead who had her reconditioned and fitted with a powerful new 6-cylinder Standard petrol engine. Kept by Lord Birkenhead until he died in 1930, her next owner was Mr. Claude Grahame-White, the pioneer aviator and aeronautical engineer, although he resold her to a Belgian before the Second World War. Surviving the War, she disappears from record around 1950, presumably scrapped.