In November 1714, Walker was appointed Commissioner of Customs. He changed the post for that of Surveyor General of crown lands in October 1731, as the latter post did not disqualify him from sitting in the House of Commons. He went first into Parliament at the age of 69. He was returned unopposed as Member of Parliament for West Looe as a government nominee at a by-election on 26 January 1733. He made his only known speech in 1733, when as a former commissioner of customs he defended the then commissioners against attacks on them by the Opposition. He did not stand at the 1734 British general election but was returned unopposed as MP for Plympton Erle at a by-election on 21 February 1735. At the 1741 British general election he was returned unopposed as MP for Helston. He did not stand in 1747.
