Members of Monty Python are being sued by one of the producers of Monty Python and the Holy Grail over royalty rights to the musical Spamalot.
The hit stage show is described on posters as being "lovingly ripped off" from the 1975 film.
But Holy Grail producer Mark Forstater claims he has been underpaid royalties since the show's launch in 2005.
Eric Idle, Michael Palin and Terry Jones are to give evidence at the High Court in London.
John Cleese and Terry Gilliam, who are abroad, are not expected to attend the hearing. Graham Chapman, the sixth member of the troupe, died in 1989.
The claim is being brought by Mr Forstater and his company Mark Forstater Productions Ltd against Python (Monty) Pictures Ltd.
Lawyer Tom Weisselberg told the judge on Friday that "for financial purposes", Mr Forstater should be treated as "the seventh Python".
He accused the Pythons of "failing to pay Mr Forstater monies he says are owed to him under an agreement reached with PMP back in 1974".
The BBC reports both sides agreed that Mr Forstater was entitled to a share in merchandising and spin-off income, but dispute the extent of his entitlement.