Simon Fuller — the man who created American Idol and the Spice Girls — is set to marry his long-term girlfriend.

The pop svengali, 47, will wed fiancee Natalie Swanston in a multi-million dollar, three-day ceremony in California’s Napa Valley at the end of the month.

A source said: “Simon is a very private man, but after dating Natalie for a few years he has finally popped the question. Money is no object so it’s going to be one hell of a party.”

Those thought to attend the plush do, include, Claudia Schiffer, Leona Lewis, the Spice Girls, David Beckham and Simon Cowell. Prince Charles and British Prime Minister Gordon Brown are expected to send good luck messages.

Fuller — whose worth an estimated $900m — was last year named one of the 100 most influential people in the world by TIME magazine.