The by-election was caused by the resignation of the sitting Unionist MP, Sir Rowland Blades.
He served in the Royal Navy and, in the period following the First World War, took part in the demilitarisation of Heligoland.
[2] The Epsom Constituency Labour Party selected Helen Keynes as their candidate to challenge for the seat.
He had been Private Secretary to the leading Liberal, Sir Herbert Samuel and the Insurance Commission.
Southby held the seat at the following General Election, against a further challenge from Parnell Kerr, who managed a swing of 1.9% to the Liberals.