The theatre has been reserved for Oct. 25. The project, however, will be funded only if a minimum of £110,000 is pledged by July 5 at 5 PM ET.

Musical director Gareth Valentine is currently scheduled to conduct a full-sized orchestra. Stars from the West End, plus guests from across the pond, will give their thanks to Sondheim, who has given his blessing to the event. No names of prospective participants are listed.

"To guarantee a seat at this once-in-a-lifetime event, book your tickets NOW by choosing the reward level that suits you," according to the Kickstarter page. "Even if you can't make the event, we'd appreciate the support, so we've thrown in a few extras, including the chance to own a hand-numbered, limited-edition artwork from actor and renowned caricaturist Clive Francis, souvenir brochures signed by the cast, annual memberships to the Stephen Sondheim Society, and even Sondheim-inspired mugs!"

Any profits from the gala will be donated to The Silver Line – the helpline for older people established by Dame Esther Rantzen DBE. This charity "provides invaluable assistance to vulnerable older people, helping to break through the stigma of loneliness and isolation, and tackling the problems of abuse and neglect."

For more information about the Kickstarter campaign, click here.