West End show Hairspray has won a record seven awards at the Theatregoers' Choice Awards.
Michael Ball has been appearing in musicals for more than 20 years
They include best musical actress for Leanne Jones, as Tracy Turnblad, and best musical actor for Michael Ball, who plays the heroine's mother, Edna.
Play Equus won three awards including best London newcomer for star Daniel Radcliffe, of Harry Potter fame.
Prizes will be presented at a concert and awards show at London's Lyric Theatre on Sunday.
Best musical actress: Leanne Jones
Best musical actor: Michael Ball
Best supporting musical actress: Tracie Bennett
Best supporting musical actor: Ben James-Ellis
Best director: Jack O'Brien
Best choreographer: Jerry Mitchell
Best new musical
Other big name winners include veteran performers Sir Ian McKellen, Dame Maggie Smith and Diana Rigg, as well as comedian Lee Evans.
Joseph and the Technicolor Dreamcoat at the Adelphi Theatre, starring TV talent show winner Lee Mead, won best musical revival.
The awards were voted for by 25,000 people on the website of organisers Whatsonstage.com.
The production of Hairspray, at the Shaftesbury Theatre, also won best new musical.
Based on a 1988 film by maverick US director John Waters, Hairspray is the story of an overweight girl growing up in 1960s Baltimore.
Ball, 45, who has been appearing in musicals for more than 20 years, said he was "thrilled to bits" with his award.
"It's so great that people love Edna - she's been very good to me," he added.
Earlier this month Hairspray received 11 nominations for the Laurence Olivier Awards, which will be announced at a London ceremony on 9 March.
Peter Schaffer's Equus, in which Radcliffe made his stage debut, won best play revival for its eight-week run at the capital's Gielgud Theatre last year.
Racy pre-production publicity photos of a naked Radcliffe helped win it the theatre event of the year award.
The 18-year-old Harry Potter star stripped off in the play for the role of stable boy Alan Strang, who has an erotic relationship with his horses.
"Playing the role of Alan Strang will remain one of the greatest experiences of my life," he said.
A new version of the play, starring Lily Allen's brother, Alfie, and thespian Simon Callow is currently on a UK tour.
Lee Evans, who will not be at the ceremony, has received his award
Sir Ian McKellen won the best actor in a play award for King Lear at the New London Theatre, beating Star Trek star Patrick Stewart in Macbeth, at the Gielgud, which won best Shakespearean production.
Best supporting actor in a play was won by Lee Evans for The Dumb Waiter.
Dame Maggie Smith won best actress in a play for The Lady From Dubuque.
Best supporting actress in a play went to Dame Diana Rigg for her role in Samuel Adamson's adaptation of Pedro Almodovar's film, All About My Mother.