Studying at Rose Bruford College of Theatre and Performance, Delve appeared in a large number of theatrical productions, including She Stoops to Conquer, Twelfth Night (as Sir Andrew Aguecheek) and as one of the two Clowns in The 39 Steps. Delve also made a number of screen appearances, playing Sam Carne in the original series of Poldark, Will Codsall in A Horseman Riding By and the Herald in Jangles, as well as guest roles in Blackadder and Casualty. He also had a role as Alec in the film Diamond Skulls. Making his musical debut as Thénardier in Les Misérables, Delve played a large number of stage musical roles, including Mr. Sowerberry in the London Palladium production of Oliver!, Firmin in The Phantom of the Opera, Sir Danvers Carew in Jekyll & Hyde and Audrey II in Little Shop of Horrors.