Leslie John Comrie (1893-1950) was born at Pukekohe, near Auckland, New Zealand, on 15 August 1893. He attended Auckland University College, and graduated M.A. with honours in 1916. He joined the New Zealand Expeditionary Force in 1917, and sailed from Wellington early the following year. During the voyage, Comrie plotted the track of the vessel, which was supposed to be secret, by using an astronomical method he had devised for establishing position at sea. On reaching Europe, he served on the Western Front, where he was wounded and lost his left leg. During his convalescence, he saw a Brunsviga mechanical calculating machine demonstrated, and as a consequence became interested in the use of machine calculation in place of tabular logarithmic methods.

In 1920 Comrie took up the Isaac Newton Studentship at St John's College, Cambridge, presenting his Ph.D. thesis on planetary occultations and the phenomena of Saturn's satellites in 1923. During his years at Cambridge, he was active in creating the Computing Section of the British Astronomical Association, becoming the first Director of the Section. He also founded, and then edited, the Handbook of the B.A.A., which first appeared in 1922.

Comrie held Assistant Professorships at American universities from 1923 until 1925, when he returned to England to join H.M. Nautical Almanac Office. He became the N.A.O.'s Deputy Superintendent in 1926, and succeeded P.H. Cowell as superintendent in 1930. While at the Office, Comrie oversaw the total reorganisation and modernisation of its methods. At the heart of these reforms was the increased use of machines to calculate ephemerides, replacing the logaritH.M.S. that had been employed since Nevil Maskelyne's time. Comrie was able to use the developments in desk calculating machines, punched card machines and later the National Accounting Machine to revitalise the Office and enhance the accuracy and scope of the 'Nautical Almanac'. However, his unconventional approach to his work led to tensions, and he was summarily suspended from duty by the Admiralty in August 1936, as Comrie reported it 'due to profound differences with his superiors on methods of procedure'.

Following his subsequent resignation, Comrie set up the company the Scientific Computing Service in Bedford Square, which offered a unique mathematical service to the nation and, during the Second World War, to the Allies. In his final years he concentrated on the perfection of mathematical tables, and in 1949 Chambers published Comrie's 'Six Figure Mathematical Tables', generally considered to be the most accurate ever published, the figures having been entirely machine-generated by the Scientific Computing Service. He also produced seven- and eight-figure tables. He was elected a Fellow of the Royal Society in 1950, and died at Greenwich on 11 December 1950.