Longden was born in the West Indies, the son of a Methodist missionary, and was educated at Kingswood School, Bath, Somerset.

An introduction to Seymour Hicks saw him start acting on the legitimate stage, beginning with a walk-on part in Old Bill, MP.

He signed a contract with Gaumont British Pictures to write and act, earning a notable success with Alfred Hitchcock's Blackmail (1929).

A company called Highway Productions was formed with Frederick Ward[6] and a capital of £10,000 but the film was not made.

[7] Longden returned to Britain where he continued to work steadily in theatre (including playing Inspector Hornleigh, a popular radio detective of the period, at the Prince's Theatre, Shaftesbury Avenue, in 1938[8]) and film (including An Honourable Murder (1960), an adaptation of Shakespeare's "Julius Caesar", in which he played tycoon 'Julian Caesar').