He was styled Sir Ian Gilmour, 3rd Baronet from 1977, having succeeded to his father's baronetcy, until he became a life peer in 1992.

The family had land in Scotland and he inherited a substantial estate and shares in Meux's Brewery from his grandfather, Admiral of the Fleet, the Hon.

The Daily Telegraph wrote that his editorship had livened up the magazine "publishing new writers such as Bernard Levin and Katharine Whitehorn and taking a strong liberal reforming stance on moral issues such as the death penalty, abortion and homosexuality; he also castigated Eden over Suez.

[5] Gilmour espoused the Arab cause when it was less popular in progressive circles than it later became and supported it throughout his years in the House of Commons, where his chief ally was Dennis Walters who was chairman of the Conservative Middle East Council.

He replaced Carrington in January 1974 to join Heath's Cabinet as Defence Secretary, but lost his position after Labour won the most seats in the general election at the end of February.

[1] With Chris Patten, he wrote the Conservative Party manifesto for the October 1974 election – a second loss, by a wider margin.

[1] He co-chaired with Carrington the Lancaster House talks, which led to the end of Ian Smith's government in Rhodesia, and the creation of an independent Zimbabwe under Robert Mugabe.

During a lecture at Cambridge in February 1980, Gilmour contended, "In the conservative view, economic liberalism à la Professor Hayek, because of its starkness and its failure to create a sense of community, is not a safeguard of political freedom but a threat to it.

[citation needed] Gilmour remained on the backbenches until 1992, and opposed many Thatcherite policies, including the abolition of the Greater London Council, rate-capping and the poll tax.

[1] In 1989, he was considered by discontented backbenchers as a possible future leader; in the event, he supported Sir Anthony Meyer in his leadership challenge in December 1989.

He also wrote the books The Body Politic (1969), Britain Can Work (1983), Riot, Risings and Revolution (1992), and The Making of the Poets: Byron and Shelley in Their Time (2002).

Lord Gilmour died from complications of a stroke and pneumonia on 21 September 2007, aged 81, at West Middlesex Hospital, Isleworth, Greater London.