Whitnall began his career in
West End musical
Elvis in 1977 after winning the role in an open call audition. He has starred in many West End musicals including
Grease,
The Rocky Horror Show, and ''Good Rockin' Tonight''. After making TV appearances for the musicals he was involved in, he began a career in television - presenting (and writing for) the BBC Schools series, "The Music Arcade" (with
Lucie Skeaping), "Music Time", "Time and Tune", "Music Workshop", and "Let's Sing". He also began making appearances as an actor, playing Jake in ITV children's drama
The All Electric Amusement Arcade and Paul in
Play for Today episode
Not for the Likes of Us. Whitnall is also known for providing many voice-overs and vocals for TV commercials, animations, and jingles. From the late 1980s to the channel's demise in 2000, he was an announcer on
The Children's Channel, also providing the voice to the station's early 1990s mascot Link Anchorman. He was also the voice for
Woolworths mascot Keith the Alien in 1998. In 1990, he succeeded
Tyler Butterworth in the role of alien Angelo in Children's sci-fi sitcom
Mike and Angelo. He portrayed the character for 10 series, until the show's end in 2000. Whitnall's theatre play
The Sociable Plover, first performed at
Old Red Lion Theatre in 2005, for 'innovation and excellence in new writing' at the 2009 Edinburgh Festival Fringe. The show opened at London's Duchess Theatre the following December and toured the United Kingdom through 2010. The piece was nominated in two separate categories in the 2010 Laurence Olivier Awards and won the 'Best Entertainment' category. In 2012,
BBC Four screened Whitnall's 90-minute drama
Best Possible Taste: The Kenny Everett Story, which examined and celebrated the life of
Kenny Everett. It was directed by
James Strong, produced by Paul Frift and starred
Oliver Lansley and
Katherine Kelly. For it, Whitnall won the Breakthrough Talent Award in the 2013 BAFTA Television Craft Awards.{{cite web During 2014, Whitnall joined the cast of the
CGI version of the British TV series
Thomas & Friends, providing the voices of the characters
Timothy,
Reg, Mike, Jerome,
Oliver the Excavator and the UK version of
Max. ==Personal life==