 Thompson was born in Kensington, and educated at Colet Court, St Paul's School and Caius College, Cambridge, where he read oriental (Hebrew and Aramaic) languages.In 1918 Mesopotamia fell into British hands, and the trustees of the British Museum applied to have an archaeologist attached to the army in the field to protect antiquities from injury.As a captain in the Intelligence Service serving in the region and a former assistant in the British Museum, R. C. Thompson was commissioned to start the work.