 After military service during the First World War, Mosley was one of the youngest Members of Parliament, representing Harrow from 1918 to 1924, first as a Conservative, then an independent, before joining the Labour Party.At the 1924 General Election he stood in Birmingham Ladywood against future Prime Minister Neville Chamberlain, coming within 100 votes of beating him.Mosley returned to Parliament as Labour MP for Smethwick at a by-election in 1926 and served as Chancellor of the Duchy of Lancaster in the Labour Government of 1929–31.