The eldest son of Walter Phillimore, he was educated at Westminster School then Christ Church, Oxford.
Living in London, Phillimore became active in the Liberal Party, standing unsuccessfully for Ripon at the 1895 United Kingdom general election.
He served as the Progressive Party secretary for Marylebone, and was elected to the civil parish council of Saint Pancras (covering at a lower tier than the relevant Metropolitan Borough from Kings Cross to Camden Town).
He stood unsuccessfully in St Albans at the December 1910 United Kingdom general election.
During World War I, Phillimore volunteered at the Hôpital Temporaire d'Arc-en-Barrois, an evacuation hospital in France.