Dennis Sydney V. Castle was born in Wandsworth, London, on 16 August 1914, was educated at Warwick School and Regent Street Polytechnic, and joined a solicitor's office in 1932. His friend Justin Long, who would later become Parliamentary Correspondent for the Financial Times, encouraged his writing talents, and in 1935 he joined the Amalgamated Press as a sub-editor, working on women's magazines Oracle and Miracle, where among other duties he wrote the problem pages and horoscopes.
His sense of humour brought him to the attention of group editor Stanley Gooch, who had him transferred to the AP's comics in 1938. The Knock-Out was then in preparation, and the dummy included strips based on celebrities like Flanagan and Allan alongside original comic creations like Hugh McNeill's Our Ernie. Castle didn't think the mix worked, and created a new title, Radio Fun, for the celebrity strips. The new title was launched on 13 October 1938, with Castle as its editor, just eight weeks after his transfer to comics. His showbiz contacts - he played cricket with a number of radio stars in the Concert Artists Association - helped him find willing subjects for comic strips.
He volunteered for the Army at the outbreak of the Second World War. The Army, thinking he was the editor of the Radio Times, assigned him to public relations in Delhi, but after the truth became apparent he was made a Captain and posted to Simla as Entertainment Officer. He organised touring shows throughout India featuring stars like Vera Lynn, Noel Coward and John Gielgud, and was promoted to Major.
When he was demobbed in 1946 the AP could not offer him his old job back, and he was paid off with a year's salary. Having caught the performing bug, he went into television. He wrote and appeared in pantomimes with Jack Hulbert, performed in the pilot of the Goon Show, and acted in the controversial TV play Scum in 1978. He also wrote two novels, and Sensation Smith of Drury Lane, a biography of his maternal grandfather, a theatrical designer. He lived in Brighton for many years with his wife Maria, whom he had married in 1939, and died in Richmond upon Thames, Surrey, on 27 February 1993.