Trainor earned critical accolades for his appearance in the special flash-back episode that launched the 2014 second series of Channel 4's Utopia.
Trainor played Jonesy, a savant with pervasive developmental disorder in the first production of Lost Monsters by Laurence Wilson at the Everyman Theatre, Liverpool in 2009.
Billy's initial betrayal at the hands of his closeted lover and, later, that of society in the form of committal for aversion therapy, leads ultimately to the character's imprisonment when he kills his treating doctor in an encounter in a gay bar.
[7] In 2011, Trainor starred as Bertie Wooster in the revival of By Jeeves, a musical by Andrew Lloyd Webber and Alan Ayckbourn, at the Landor Theatre in Clapham, London.
[8] Trainor returned to his native Northern Ireland in 2012 to appear in the ensemble play Titanic (Scenes from the British Wreck Commissioner's Inquiry 1912) by Owen McCafferty at the new MAC Theatre in Belfast.