Career
He unsuccessfully contested the 1929 general election as a Liberal Party candidate in the Blaydon constituency in County Durham. When the Liberal Party divided in 1931 over whether to support Ramsay MacDonald"s National Government, Magnay joined the pro-government Liberal National faction. At the 1931 general election he was elected as Member of Parliament for Gateshead, a previously safe seat for the Labour Party, but where two Labour MPs had died that year.
He defeated the influential union leader Ernest Bevin, who was the Labour candidate.
He held the Gateshead seat until his defeat at the 1945 general election by the left-wing Labour candidate Konni Zilliacus.