O’Sullivan was an agent and partner at Troika for 13 years and previously worked in casting with well-known UK casting directors John and Ros Hubbard, whom he now represents.
He brings with him clients including Cannes Best Actress winner Emily Beecham, BAFTA and Olivier Award-winner Noel Clarke, Golden Globe nominee Colm Meaney, BAFTA-winner Rebecca Front, BAFTA-nominated Nikki Amuka-Bird, Sarah Bolger, Tom Felton, Ulrich Thomsen, Cannes Best Actress-winner Jodhi May, Elyes Gabel and Mark Stanley.
Martin-Sperry worked closely with O’Sullivan at Troika and alongside him represents actors including SAG winner and nominee Adewale Akkinuoye-Agbaje, Sam Palladio, Sharon Rooney and Ivanna Sakhno.
42 partner Kate Buckley said: “We could not be more delighted that Gary has joined us. He brings with him an impeccable reputation, a fantastic client list