He was a Member of Parliament (MP) for most of the years from 1906 to 1915, when he was elevated to the peerage and served as Lord Chancellor under H. H. Asquith from 1915 to 1916.

His father began life as a young agricultural labourer, and rose to teach chemistry at the Imperial College of Science and Technology.

Buckmaster returned to the Commons the following year, when he was elected at a by-election in October 1911 for the safe Liberal seat of Keighley in Yorkshire.

Buckmaster was also Counsel to the University of Oxford from 1911 to 1913, Director of The Press Bureau, 1914 to 1915, and a member of The Interallied Conference on Finance and Supplies.

He was sworn of the Privy Council and raised to the peerage as Baron Buckmaster, of Cheddington in the County of Buckingham.

He only appointed two High Court judges—Peterson and McCardie—and no new King's Counsel, on the grounds that junior barrister engaged in war service would be disadvantaged.

Sitting judicially, he gave the decision in Cook v Deeks, a notable company law case.

His niece, Hilda Buckmaster was also active in politics, three times standing as a parliamentary candidate for the Liberal Party.