Later in 1944, Beveridge, who had recently joined the Liberal Party, was elected to the House of Commons in a by-election to succeed George Charles Grey, who had died on the battlefield in Normandy, France, on the first day of Operation Bluecoat on 30 July 1944. Beveridge briefly served as Member of Parliament (MP) for the constituency of Berwick-upon-Tweed, during which time he was prominent in the Radical Action group, which called for the party to withdraw from the war-time electoral pact and adopt more radical policies. However, he lost his seat at the 1945 general election, when he was defeated by the Conservative candidate, Robert Thorp, by a majority of 1,962 votes.