[citation needed] When the Liberals came to power in 1905 under Sir Henry Campbell-Bannerman, Pease was appointed a Junior Lord of the Treasury (government whip).

After H. H. Asquith became Prime Minister in 1908 he was promoted to Parliamentary Secretary to the Treasury (Chief Whip) and sworn of the Privy Council.

Apart from his political career Pease was Deputy Chairman of the Durham Coal Owners Association and vice-chairman of the Durham District Board (under the Coal Mines Act 1930), a director of Pease and Partners Ltd and other colliery companies, Chairman of Durham Coke Owners, director of the County of London Electric Supply Company, Chairman of South London Electric Supply Corporation, of the Tees Fishery Board, and of the Trustees of the Bowes Museum.

The main part of the Pease diaries cover the years 1908–1915 and a volume dealing with the years 1908–1910 have been published by Cameron Hazlehurst and Christine Woodland as A Liberal Chronicle: Journals and Papers of J A Pease, 1908–1910; The Historians Press, London, 1994.

[citation needed] Lord Gainford married Ethel, daughter of Sir Henry Havelock-Allan, 1st Baronet, in 1886.