Michael Colvin was born to Captain Ivan Beale Colvin RN and Joy Arbuthnot. He had a brother, Alistair Colvin, four years his junior. He was educated at West Downs School in Winchester, Eton College; and the Royal Military Academy at Sandhurst. Joining the Grenadier Guards at 18, he served in Berlin, Suez and Cyprus, emerging as a captain. After studying at the Royal Agricultural College at Cirencester, he initially worked for four years in advertising with the agency J Walter Thompson, then for 14 years as a director of Accrep Ltd, a property investment firm.
Active in local government at first, he was an elected member of Tangley parish council, Andover rural district council and Hampshire County Council. He had left Hampshire local government by the mid-1970s
His first parliamentary seat was Bristol North West, which he gained from Labour in 1979, when Margaret Thatcher achieved power, but he was then considered to be one of the "wets", and thus under Thatcher likely to remain a backbencher.
Colvin showed political ambivalence, however, he urged the creation of a new centre party on the one hand, but also called for privatisation of NHS. In 1983, he switched to the newly created and much safer seat of Romsey and Waterside, near Southampton. As a Cayzer son-in-law, he opposed the phasing out of tax allowances on new shipbuilding and urged a larger, more modern merchant marine fleet. He opposed the slicing off of BA's routes just when it was becoming successful. He favoured easier conditions for pub licencees.
Opposed to bans on foxhunting, Colvin was the chairman of the Council for Country Sports from 1988, Colvin rejected gun-control; he was a leading figure, following the Hungerford and Dunblane massacres in the "gun lobby". He was a defence and aviation specialist, serving on the Defence Select Committee, which he chaired from 1995 to 1997, leaving it in January 2000. However, he was not politically consistent with the right-wing of the Conservatives; he was liberal on abortion and favoured free eye and dental treatment, In 1989 he sponsored a Private Member's Bill which became the Computer Misuse Act 1990.
Colvin became the chairman of the Conservative Foreign and Commonwealth Affairs Committee. He supported the South-African-backed anti-SWAPO white forces in Africa and endorsed the regime in Namibia in 1981. In his Guardian obituary of Colvin, Andrew Roth wrote that the MP "was also a somewhat secretive former propagandist for apartheid South Africa". He defended the whites of southern Africa, accepting invitations to visit South Africa, then under apartheid, and Bophuthatswana, a Bantustan ('homeland') set up for blacks by the South African government. He urged that the 'homelands', which were not internationally recognised, should be accepted. Although he supported reformist Denis Worrall's election campaign in 1987, the following year he criticised the BBC for broadcasting the concert tribute to Nelson Mandela. Colvin visited Bophuthatswana again, and Angola, in 1989 as a guest of UNITA, an organisation backed by the CIA and South Africa. Connected to the Strategic Network International (SNI), a lobbyist front set up in 1985 to campaign against the imposition of economic sanctions against South Africa, Colvin was involved in finding sympathetic Conservative MPs to visit the 'homelands' on expenses paid trips. The Conservative activist Derek Laud was involved in SNI and was responsible for recommending Colvin to the group.
In 1991, Colvin became a consultant to SNI (at £10,000 a year), in succession to Neil Hamilton. Colvin, with Conservative colleagues John Carlisle and David Atkinson were among members of SNI sent to watch the peace process in Angola during 1992. SNI dissolved the following year. His consultancy with SNI was not declared, and when the connection became known in 1994, the media linked the issue to then on-going Cash-for-questions affair: "It was not registered. It is an oversight which I regret", Colvin said. At this time, among 11 Conservative MPs, he was found by the Commons Select Committee on Members' Interests to have failed to declare, as a Lloyd's 'Name', details of his syndicate's activities, specifically the areas of insurance underwritten. He was a friend to lobbyists such as Ian Greer, more directly implicated in the cash for questions scandal, which led to Hamilton's disgrace. Later, Colvin became a director, with Derek Laud, of the Laud Ludgate lobbying organisation.
He married Nichola Cayzer, the daughter of William Cayzer, Baron Cayzer, an executive in the British and Commonwealth shipping company. The couple had three children; two daughters and a son.
Colvin and his wife died in a fire at their house, Tangley House, near Andover in February 2000. The following by-election led to the Liberal Democrat gaining the seat with their candidate Sandra Gidley being elected.