He later switched back to the Liberal Party to serve as Under-Secretary of State for War under Sir Henry Campbell-Bannerman from 1905 to 1908.

Lymington was born in Hurstbourne Priors, Hampshire, the eldest son of Isaac Wallop, 5th Earl of Portsmouth, and his wife Lady Eveline Alicia Juliana Herbert, daughter of Henry Herbert, 3rd Earl of Carnarvon.

From 1905 to 1908, Lord Portsmouth served as Under-Secretary of State for War in the Liberal administration of Sir Henry Campbell-Bannerman.

[3] A passionate Protestant he chaired the United Protestant Demonstration in London on 29 January 1900 which resolved “to uphold and maintain the Protestantism of the nation and to demand the suppression of the Mass and the Confessional in the Established Church.”[4] In 1908, he bought Guisachan House and its huge deer estate in Glen Affric from Baron Tweedsmouth.

He died in December 1917 at Whitchurch, aged 61, and was succeeded in the earldom by his younger brother, John.