Forbes trained at RSAMD in Glasgow (now The Royal Conservatoire of Scotland).

Theatre includes: Much Ado About Nothing and The Tempest (Jamie Lloyd Productions at Theatre Royal, Drury Lane); Laughing Boy (Jermyn Street Theatre/Bath Theatre Royal); Jekyll & Hyde (Royal Lyceum Edinburgh & Tour); Farm Hall (Jermyn Street Theatre/Bath Theatre Royal & tour); Newsies! (Troubadour Theatre); The Taxidermist’s Daughter (Chichester Festival Theatre); The Magician’s Elephant, The Boy in the Dress, Macbeth, Hamlet, The Comedy of Errors, Twelfth Night, The Histories, As You Like It, Romeo and Juliet, The Taming of the Shrew, The Grain Store, Morte d’Arthur, The Pilate Project, Ahasverus, Tender Thing (RSC); Summer and Smoke (Almeida/Duke of Yorks); Little Shop of Horrors (Regent’s Park); Travesties (Menier Chocolate Factory/Apollo Theatre); Mr Foote’s Other Leg (Hampstead/Theatre Royal Haymarket); Doctor Faustus (Duke of York’s); Macbeth, Richard II, The Ruling Class (Trafalgar Studios/Jamie Lloyd Productions); Big Fish (The Other Palace); King Lear (Liverpool Everyman/Young Vic/Headlong); The Lion, The Witch and the Wardrobe (Kensington Gardens); Bartholomew Fair, The Merry Wives of Windsor, Boudica (Shakespeare’s Globe); Dumbstruck, Terror (Lyric Hammersmith); Art, The Breathing House, Stiff (Lyceum Edinburgh); As You Like It,Romeo and Juliet (RSC Residency in New York); Life of Stuff (Donmar); Laurel and Hardy (Edinburgh Festival/Wellington Festival NZ); The Trick is to Keep Breathing, The Real World, Cinzano (Tron Theatre Glasgow).