Harry Potter stars Daniel Radcliffe and Rupert Grint both won gongs at the WhatsOnStage Awards which were dominated by T he Book Of Mormon.
The award-winning show, by South Park creators Trey Parker and Matt Stone, won b est new musical, best actor in a musical, and best supporting actor and actress in a musical.
Radcliffe, who was named b est actor in a play for his role in The Cripple Of Inishmaan, said: "I am deeply honoured to receive this prestigious award and I accept it on behalf of the whole cast who together helped make this production of The Cripple Of Inishmaan a truly joyous experience for me as an actor.
"I'd also like to thank Michael Grandage for his leadership and inspirational direction, and I'm absolutely thrilled to now be given the opportunity to take Martin McDonagh's achingly witty and poignant play to Broadway."
Grint was named the London newcomer of the year for his West End debut in Mojo - an award which Radcliffe won previously for Equus.
The winners, decided by a vote of theatregoers and announced at a ce remony at the Prince of Wales Theatre in central London, also included David Walliams who won the best supporting actor in a play award for his role in A Midsummer Night's Dream.
Dame Helen Mirren, recently honoured with the Bafta Fellowship, was named b est actress in a play for her role as Queen Elizabeth II in The Audience.
In a pre-recorded acceptance speech, she said: " I'm so thrilled to receive this. I'm honoured that it was voted for by the public, that's the most wonderful thing."
The A udience also received best new play for Peter Morgan and best supporting actress for Haydn Gwynne, who played Margaret Thatcher in the drama based on the Queen's regular meetings with the prime ministers who have held power during her reign.