Dempsey's first role came at the age of 15, when he appeared as Peter Pevensie in the
BBC's adaptation of
The Lion, the Witch and the Wardrobe in 1988. The following year, he appeared in the adaptation of
Prince Caspian and the Voyage of the Dawn Treader. His subsequent TV appearances have included
Doc Martin,
Dracula,
Sherlock Holmes (
The Last Vampyre),
Crime Traveller,
Island at War and
Egypt. He made his professional stage debut in the role of Jack in the original London production of the musical
Into the Woods with music and lyrics by
Stephen Sondheim at The Phoenix Theatre. After training at the
Guildhall School of Music and Drama he starred as Nick Piazza in the original cast of
West End musical
Fame and played
Ugly in the original UK production of
Honk! He has since performed in a variety of roles in television, film and on stage with the
Royal Shakespeare Company, the
Royal National Theatre,
Michael Grandage Company,
Frantic Assembly and
Propeller. In the
Michael Grandage West End production of ''
A Midsummer Night's Dream'', he played
Peter Quince. In the 2015 London revival of TS Eliot's
The Cocktail Party he played Edward Chamberlain, directed by Abby Wright. In 2022, Dempsey appeared as Nicholas II of Russia in
Doctor Who and as
Paul Crouch in the world premiere, at London’s
Almeida Theatre, of the musical
Tammy Faye, written by
Elton John,
Jake Shears, and
James Graham. == Filmography ==