(1893-1965) 19th Lord Sempill, engineer, aviator

William Francis Forbes-Sempill was born on the 24th September 1893 at Devonport. He was educated at Eton College and from 1910 to 1913 he was an engineering apprentice in the workshops of Rolls-Royce Ltd at Derby. At the outbreak of war in 1914 Sempill joined the Royal Flying Corps (RFC) as an engineer second-lieutenant at Farnborough, and learned to fly at the Central Flying School at Upavon. In 1916 he transferred to the Royal Naval Air Service as flight commander, and on 1 April 1918 to the newly formed Royal Air Force as a lieutenant-colonel. He was then promoted colonel. He retired from the RAF in June 1919.

In June 1918 Sempill went as a personal assistant and advisor to Sir Sefton Brancker and Sir Henry Fowler on a royal aircraft commission to the United States. This stood him in great stead, as in 1921 he was invited to lead a technical mission to Japan to set up an imperial Japanese naval air service. Sempill's success in Japan led to his being invited to head similar missions successively to Greece, Sweden, Norway, Chile, Brazil, and Argentina and to be awarded numerous foreign decorations. Back in England in 1924 Sempill began twelve years of enthusiastic flying as an unofficial ambassador for British aviation at home and overseas. Flying a succession of light aeroplanes he competed—without success—in the king's cup air races of every year from 1924 to 1930.

Sempill had joined the Royal Aeronautical Society in 1917; in 1926 he was elected chairman of its council, and from 1927 until 1930 he was the society's president. Sempill was active in numerous other aeronautical interests—on the Aeronautical Research Council, on the councils of the Air League and the Navy League, as deputy chairman, and then chairman, of the London chamber of commerce between 1931 and 1935, as president of the British Gliding Association from 1933 to 1942, and as president of the Institution of Production Engineers from 1935 to 1937

Sempill succeeded his father as Lord Sempill on 28 February 1934, and was a representative peer for Scotland from 1935 to 1963. He re-joined the naval air service in 1939 and retired in 1941. He died in Edinburgh on 30 December 1965 and was succeeded by his eldest daughter, Ann Moira (1920–1995).