Michael Crawford, star of Andrew Lloyd Webber's new musical Woman in White, told Prince Charles the royal premiere on Monday night was "nerve-racking".
Crawford will don a fat suit for every performance
Crawford, 62, plays villain Count Fosco in the production directed by Trevor Nunn at the Palace Theatre in London.
The Prince, accompanied by Camilla Parker Bowles, met the stars backstage - the £4m musical is adapted from Wilkie Collins' Victorian thriller.
Crawford last appeared in the West End in Phantom of the Opera in 1986.
"The Prince said he hopes it goes all right and I said 'I hope so too'," said Lloyd Webber.
Leading lady Maria Friedman said the Prince loved the show.
"It was wonderful. It's always nerve-racking," he said of his return.
Crawford plays a charismatic Italian count, alongside actress Maria Freedman as the heroine.
His other stage credits include Barnum and The Music of Andrew Lloyd Webber world tour.
But his last Broadway production Dance of the Vampires closed after just seven weeks, with losses of £7.5m.
Lord Lloyd-Webber's musical pedigree includes Joseph and the Technicolor Dreamcoat, Cats and Starlight Express. His most recent show was Bombay Dreams, which has transferred to Broadway.
Monday's royal performance was staged in support of The Prince's Trust charity - Lord Lloyd-Webber told Prince Charles he would be inviting six young people for a day's work experience at the Palace Theatre, where the show is running.