He was employed at the Natural History Museum in London from 1926 to 1948, specialising in the biology of algae, after which he worked for the British Foreign Office until 1954.
[1] During the Second World War he joined the Royal Naval Volunteer Reserve and rose to the rank of Paymaster Commander.
In 1941 he was in charge of the research sub-section with responsibility for captured documents, and later he became Head of Technical Intelligence.
[4][5] During the Second World War he worked at Bletchley Park, allegedly invited there after the Ministry of Defence confused the word "cryptogamist" with "cryptogramist".
[6][7] At Bletchley his technical expertise allowed him to salvage a waterlogged codebook which helped crack the Enigma code.