The Australian wrote the music and lyrics for the adaptation of the Roald Dahl classic about a little girl with strange powers, which won the Evening Standard Theatre Award for best musical.
Minchin, whose parents had flown in from Australia for the opening last night, said he was in a state of “disbelief” at the success of the Royal Shakespeare Company show, which has transferred from Stratford-upon-Avon.
He said: “It’s incredibly exciting and all the things you might think of, and then add 80 per cent.”
Downton Abbey actor Hugh Bonneville said: “Tim Minchin is a genius and it’s amazing that he won an award the other night. I feel privileged to be here.”
Also at the event was Sheridan Smith, who also won an Evening Standard Theatre award for best actress in Flare Path and has previously won stage awards for her starring role in the musical Legally Blonde. She was one of the first to her feet in a standing ovation to the cast last night.