On 29 January 1914, he succeeded Frederick Bullock as Assistant Commissioner "L", in charge of the Legal Department of Scotland Yard.
During the First World War, he spent most of his time dealing with the control of aliens, and in 1919 he was appointed Companion of the Order of the Bath (CB).
[1] On 6 November 1922, Bigham and his colleague, Assistant Commissioner Frank Elliott, were sent a box of chocolate éclairs poisoned with arsenic.
Luckily, they were suspicious and did not eat them, and Walter Tatam, who had a history of mental problems, was later found guilty of attempted murder.
He was appointed Knight Commander of the Order of the British Empire (KBE) in the Metropolitan Police Centenary Honours of 3 June 1929.