Walker rose through the ranks of the Conservative Party's youth wing, the Young Conservatives. He was a branch chairman at the age of 14, and later National Chairman. He fought the Parliamentary seat of Dartford in the general elections of 1955 and 1959, being beaten each time by Labour'sSydney Irving. Walker was appointed to the Order of the British Empire as a Member in the 1960 Birthday Honours for political services. Within four years of his election to Parliament in a by-election in 1961, he had entered the Shadow Cabinet. He later served under Prime Minister Edward Heath as Minister of Housing and Local Government, Secretary of State for the Environment, the first person in the world to hold such a position, and Secretary of State for Trade and Industry. From late 1974 to February 1975, Walker served as Shadow Defence Secretary. When Margaret Thatcher became the party leader, Walker did not serve in her Shadow Cabinet. But when the party to power in 1979, he returned to the Cabinet as Minister of Agriculture, Fisheries and Food, in 1979. He later served as Secretary of State for Energy. Whilst at the Department for Energy he played an important role in the Government's successful opposition to the 1984–85 miners' strike. Walker then served as Secretary of State for Wales between 1987 and 1990. Although the role of Welsh Secretary was ostensibly one of the most junior jobs in the Cabinet, Walker claimed it gave him more influence as it gave access to key economic committees. He stood down from the Cabinet shortly before Thatcher herself was ousted in 1990. Though he had previously been a close ally of Heath's and was generally considered to be on the left of the party, he was nevertheless one of the longest-serving Cabinet members in Thatcher's government. In October 1985, however, he had hit out at Thatcher's reluctance to inject money into the economy in order to ease mass unemployment, speaking of his fears that she could lose the next general election if unemployment did not fall. However, the Tories were re-elected in 1987, by which time unemployment was falling. As noted above, Walker's 1970 appointment as Secretary of State for the Environment was notable in that he became the world's first Environment Minister, and was thus a source of considerable interest at the 1972 Stockholm Conference. The creation of the Department of the Environment came in response to the growing environmental concerns of the 1960s, and one of Walker's immediate concerns was to clean up the nation's waterways. The measures put in place have had substantial results for river life. For instance, the Thames was declared biologically dead in 1957 but today many species of fish thrive in the river, including wild salmon and trout. Walker was a determined supporter of the hospice movement, becoming a patron of St Richard's Hospice in Worcester when it was founded in 1984. He campaigned determinedly for greater NHS support for St Richard's and the wider hospice movement, which is staffed largely by dedicated volunteers. During a House of Lords debate in 2000, Lord Walker stated: "Anyone who visits hospices and meets the volunteers—the people running them and guiding them—will recognise their unique spiritual and compassionate contribution to the health service." Upon his retirement from Parliament, on 8 July 1992, he was appointed a life peer as Baron Walker of Worcester, of Abbots Morton in the County of Hereford and Worcester.
Walker and his wife had five children. His son Robin Walker was elected MP for the Worcester constituency in the 2010 general election. He died at St Richard's Hospice on 23 June 2010, after suffering from cancer.
