Karl has produced/co-produced: Sinatra At The London Palladium the spectacular multimedia production directed by David Leveaux with choreography by Stephen Mear; And Then There Were None with Tara Fitzgerald at the Geilgud; the London & Sydney production of Dance Of Death with Sir Ian McKellen, Frances de la Tour and Owen Teale; Bea Arthur at the Savoy; Auntie And Me with Alan Davies and Margaret Tyzack at the Wyndham's; Michael Moore. Live! at the Roundhouse; the West End premiere of Noel Coward's Semi Monde; Kevin Elyot's Mouth To Mouth at the Albery Theatre with Lyndsay Duncan and Michael Maloney; David Mamet's Speed The Plow with Mark Strong, Patrick Marber and Kimberly Williams; Drummers by Simon Bennet and Some Explicit Polaroids by Mark Ravenhill (winner of the Evening Standard Award as Most Promising Newcomer) both directed by Max Stafford-Clark for Out of Joint; Macbeth with Rufus Sewell at the Queens Theatre; A Swell Party a celebration of Cole Porter at the Vaudeville Theatre; Timberlake Wertenbaker's Our Country's Good (nominated for six Tony Awards and received the Olivier Award for Best Play and the New York Critics' Award for Best Foreign Play); Hysteria (Best Comedy, Olivier Awards), and an adaptation of Sue Townsend's novel The Queen And I which was Out of Joint's inaugural production.

Karl continues to serve on the board of Out of Joint, the UK leading producer of new writing for the theatre.

Karl also served as a director of Renaissance Film Company. He continues to act as an independent film producer; projects under development with David Parfitt, his colleague from Renaissance include A Bunch Of Amateurs by Ian Hislop & Nick Newman and the film of Cape High by award winning writer/director Sean Mathias.