 After Margaret Thatcher became Conservative leader in 1975, Butler became one of her two Parliamentary Private Secretaries, along with John Stanley.After the Conservative victory at the 1979 general election, he served as Minister of State for Industry at the Department of Industry until 1981, and then as minister for economic development in Northern Ireland until 1984, where he called in the receivers at the De Lorean motorcar company, and finally as minister for defense procurement until 1985.He was sworn of the Privy Council in 1984, and knighted in 1986.