Idle’s surviving former colleagues — Terry Jones, Michael Palin, Terry Gilliam and John Cleese — were initially reluctant to give their approval to Spamalot, but have been mollified after a stream of royalty cheques.

Three members have shown their support for the show by agreeing to appear at the gala opening on the London stage tonight. John Cleese is the only surviving member not to attend. He is filming in Australia.

The success of the musical in New York, where it has taken more than $1 million (£537,000) a week at the Shulman Theatre, has ensured weekly royalty cheques of more than $10,000 for the rights owners of Monty Python and the Holy Grail.

Each surviving Python and the estate of Graham Chapman, who died in 1989, takes approximately 10 per cent of that figure.

Jones, who co-directed the original film, voiced the group’s unease about the project when the surviving members attended the show when it opened on Broadway.

“It is Eric’s show,” he said. “He will make more out of Spamalot than anybody has ever made out of Python. Good luck. But if we had known it was going to be such a success, we’d have gone for a better deal.” He added that he liked the songs, but found Spamalot to be “utterly pointless and full of hot air”.

Idle told The Times: “The hardest thing to do was to persuade them that this was something that would go well,” he said.

He made a breakthrough when he played them one of the new songs. “We played them The Song that Goes Like This and they cracked up. That was the secret of it.”

“It is a money-spinner for us. It will continue to be, because there is a touring version as well. It is a big opportunity,” Idle added.

Times Recommends

• Would you live on the wrong side of the Berlin Wall?
• Wish you were here, says Iraq tourist board
• Russian policeman’s corruption plea to Putin