He founded the International Tea Company's Stores, became the first chairman of the Port of London Authority, and served as Minister of Food Control during World War I. Devonport was the tenth and youngest child of George Ewbanke Kearley (1814–1876) and his wife, Mary Ann Hudson.

He worked hard for a number of years on ensuring that the more than £1m within Patriotic Fund was unlocked and made available for the purposes that it had been donated.

He was created a baronet, of Wittington in the Parish of Medmenham in the County of Buckingham, on 22 July 1908[4] and became a member of the Privy Council in 1909.

He was appointed as Minister of Food Control in December 1916 by Lloyd George and he submitted a proposal for compulsory rationing in May 1917, seemingly delayed as to protect the interests of retailers.

[10] Devonport's wartime measures for the rationing of sugar and other imported commodities were satirised by Neil Munro in his Erchie MacPherson story "The Last of the Bridescakes", first published in the Glasgow Evening News of 12th February 1917.