He was born in Dublin, the son of an Irish solicitor, and went to Rugby School in 1903 and then in 1907 to the University of Oxford, where he studied history.

He gives special attention to the political trial of Jatindra Mohan Sengupta, mayor of Calcutta, for sedition in impromptu speeches made during a brief visit to Rangoon in 1930; also to two criminal trials which became politically charged because they brought to light underlying attitudes of British merchants and army officers to Burmese people.

Collis's judgements were (according to his own analysis) too independent to be pleasing to the then British Government of Burma, arousing the particular disapproval of his superior, Booth Gravely, Commissioner of the Pegu Division.

After giving judgement in the last of these trials Collis was hastily moved to the post of Excise Commissioner.

After returning to England in 1934, he wrote many books, including Siamese White and Foreign Mud, as well as art and literary criticism.