Shelton entered politics upon his return to London in 1964, becoming that year the president of the WandsworthYoung Conservatives. He was elected to the Greater London Council to represent Wandsworth in 1967, and in 1968 he became the Chief Whip of the Conservative majority on the Inner London Education Authority. Shelton's association with Margaret Thatcher began when she became Shadow Secretary of State for Education and Science in 1967. He soon showed his independence of mind, refusing to participate in the racism directed towards his Labour opponent in the 1970 election, and becoming an early monetarist, a supporter of the European Economic Community as a trade bloc, and an advocate of parental choice in schooling. He was also a traditionalist on moral issues, a Zionist, and concerned with Greek and Polish interests. He served as Parliamentary Private Secretary to Sir John Eden, Minister of State for Posts and Telecommunications from 1972 to 1974. Shelton was one of the first people to advocate for Thatcher to succeed Edward Heath as Conservative leader, becoming second-in-command to campaign manager Airey Neave. Shelton is reputed to have organised the successful "stealth" campaign to convince backbench Conservatives on the party's right wing that by backing Thatcher in the leadership ballot they could oust Heath. After Thatcher's victory in the leadership election, Shelton became her Parliamentary Private Secretary, but resigned the following year, preferring the freedom of the backbenches. He continued his interest in education, repeatedly being elected Vice-Chairman of the backbench Conservative Education Committee, and serving as a junior minister in the Department of Education and Science from 1981 to 1983, in which role he increased computer provision in primary schools and proposed a new vocational qualification of secondary education. Shelton became an increasingly vocal critic of local government. He clashed with the left-wing leadership of his local Lambeth Council and promoted a bill in 1981 to restrain local-government spending. However, he opposed Thatcher's flagship Community Charge, because it was designed to give local authorities more independence. Shelton was known as a Thatcherite, serving on Thatcher's campaign team in the leadership election of 1989 and opposing her resignation in 1990. He was confident of retaining his seat in 1992, but, having been defeated, he received 5000 letters of thanks, mostly from people who had voted Labour.