Callow's theatrical credits include Royal National Theatre mountings of The Alchemist, Single Spies, Sisterly Feelings, Amadeus and As You Like It and productions of Chimes at Midnight, The Importance of Being Oscar, The Destiny of Me, Faust, Kiss of the Spider Woman, Melancholy Jacques, On the Spot, The Relapse, Plumbers Progress, Mary Barnes, Titus Andronicus, The Resistible Rise of Arturo Ui, The Mystery of Charles Dickens in which he appeared both in London and on Broadway and Through the Leaves. Last year he was featured as Andre, one of the overwhelmed owners of the opera house, in the film version of The Phantom of the Opera.