Career: McCallum became an assistant stage manager, but National Service interrupted his career. He made his film debut in 1957's These Dangerous Years, and appeared in numerous British movies before moving to Hollywood in the early 1960s. He landed roles in Billy Budd and The Great Escape but it was his performance as Illya Kuryakin in The Man from UNCLE that made him a household name in 1964. The series ran until 1968, and a spin-off TV movie was made in 1983. He also released four albums in the 1960s. Other major projects include Colditz, The Invisible Man, Sapphire and Steel, Mother Love, Hear My Song, and Cluedo. Since 2003, he has starred in popular American drama NCIS, playing forensics expert Dr Donald 'Ducky' Mallard.

Career: In 1956, Vaughn was signed by Burt Lancaster's production company, but was drafted into the army shortly afterwards. On his return to Hollywood, he spent the next few years playing small roles in movies and TV series such as The Ten Commandments and Gunsmoke. In 1960 he received an Oscar nomination for The Young Philadelphians and was one of The Magnificent Seven. TV show The Lieutenant followed, and he became a major global star thanks to The Man from UNCLE in 1964. Vaughn has also starred in Bullitt, The Towering Inferno, Battle Beyond the Stars, and SOB, and continues to regularly crop up on the big and small screens. He starred in as con-artist Albert Stroller in the BBC drama Hustle between 2004 and 2012, before shifting his attention to Coronation Street to appear as rich American Milton, the love interest of Sylvia Goodwin.

Career: Shatner spent years as a jobbing actor, appearing in such movies as The Brothers Karamazov and The Intruder, as well as The Twilight Zone TV series before Star Trek made him a household name in 1966. He played Captain Kirk for three years before the show was cancelled, then appeared in numerous TV shows and movies before Star Trek: The Motion Picture relaunched his career in 1979. He starred as Kirk in six more films before the character was finally killed off in 1994. He has also featured in TJ Hooker, Free Enterprise and Miss Congeniality and its sequel. Shatner returned to TV in 2004 in the series Boston Legal. In 2010, he starred in his first sitcom, $#*! My Dad Says. Away from showbusiness, he's written several sci-fi novels, recorded a number of much-criticised albums and is a champion horse breeder.

Career: After small roles in two little-seen films, Nimoy landed the lead in the 1952 movie Kid Monk Baroni. He appeared briefly in cult classic Them! before spending two years in the US Army. When he returned to acting, he supplemented his income with odd jobs. His big break came in 1965 when Gene Roddenberry offered him the part of Mr Spock in the TV series Star Trek. When the show ended, he starred in the TV series Mission: Impossible and various long-forgotten movies and TV shows. From 1979 onwards, he returned to play Mr Spock in various projects and turned to directing, making Three Men and a Baby in 1987. He died on February 27, 2015, at the age of 83.