Brian Horace Clemens (30 July 1931 – 10 January 2015) was an English screenwriter and television producer, who worked on The Avengers and The Professionals. Clemens claimed to be related to Mark Twain (Samuel Langhorne Clemens), a fact reflected in the naming of his two sons, Samuel Joshua Twain Clemens and George Langhorne Clemens. Early life Clemens was born in Croydon, Surrey, to Suzanna (née O'Grady) and Albert, an engineer, who also worked in music halls. He left school aged 14. Following national service in the British Army at Aldershot, where he was a weapons training instructor in the Royal Army Ordnance Corps, Clemens wanted to be a journalist but decided he did not have any qualifications. He was offered a job with a private detective agency, but this involved taking a training course in the city of Leeds and, as he had been away from home in London for two years, he decided he did not want to go away again. Instead, he worked his way up from messenger boy at the J. Walter Thompson advertising agency. While he was a copywriter there, he had a thriller screenplay accepted and shot by BBC TV - Valid for Single Journey Only (1955). This brought him to the attention of the Danziger brothers, independent, low-budget movie producers. TV career Writer From the mid-1950s onward Clemens was a staff writer for the Danzigers, churning out dozens of quickie scripts for assembly line 'B' movies and half-hour television series such as Mark Saber (ITV, 1957–1959; also known as Saber of London), White Hunter (ITV, 1958–1960), Man from Interpol (ITV, 1960–1961), and Richard The Lionheart (ITV, 1961–1965). He also wrote for ITC Entertainment's thriller series The Invisible Man (ITV, 1958–1959), Sir Francis Drake (ITV, 1961–1962), and Danger Man (ITV, 1960–1961; 1964–1967; also known as Secret Agent), for which he had also written the pilot. His output was so prolific during the late 1950s and throughout the 1960s that he frequently used the pseudonym Tony O'Grady. He wrote the second episode for The Avengers (but not the pilot as is often stated) in 1961 and was the script editor, associate producer and main scriptwriter for The Avengers series (ITV, 1961–1969). According to the British Film Institute's profile of him, he "brought this spirit of burlesque to his other series - most notably with Adam Adamant Lives! (BBC, 1966-1967), but also with The Baron (ITV, 1966-1967),