In 1900 he joined the 1st London Rifle Volunteers (territorial army) as a major, rising to the rank of colonel and commanding officer.

Lucan was for eighteen months a Member of Parliament (MP) for the Chertsey constituency in Surrey.

On his father’s death on 5 June 1914 he succeeded him as Earl of Lucan and in August of that year, a few days after Britain had declared war on Germany, he was elected as an Irish representative peer, enabling him to sit in the House of Lords.

He had earlier widened his father's gift of land which gave over Laleham Park for community use.

[4][5] In 1896 Lucan married Violet Sylvia Blanche Spender Clay, a daughter of Joseph Spender Clay and Elizabeth Sydney Garrett, with whom he had four children:[1] Lord Lucan died in April 1949, aged 88, succeeded in the earldom by his eldest son George through whom the title continues as at 2025.

The Dowager Countess of (Lady) Lucan died after their eldest son in 1972; her net estate at death was sworn as £26,433 that year; she lived at 40 Orchard Court, Portman Square.

From 1920 until 1928 he was one of the King's aides-de-camp, a ceremonial honour awarded to military figures which entitles the recipient to wear aiguillettes.

Lucan died in 1949 while staying at the Cavendish Hotel, Eastbourne, but by then usually lived in Westminster at 19 Orchard Court, Portman Square.