A MULTI-MILLIONAIRE said he "couldn't believe his eyes" when the well-heeled partygoers who had hired his estate for £9,000 stripped down for an orgy.

Grahame Bond was initially impressed by the extravagant masked ball-style outfits 350 guests wore to his 17-bedroom Halswell House in Somerset for a private party on Saturday night.

But he was unaware that it had been hired out by a Dutch firm who charged £65 a ticket for a party themed on the film Eyes Wide Shut, in which Tom Cruise finds himself in a high-class sex party.

The intentions became clear at around midnight, when party organiser Mike Voorvaart, of the Little Sins events company, declared: "The moment has come. The spell has begun." The signal led to the revellers stripping off to reveal fetish-style underwear and immediately starting to kiss and engage in more intimate activity.

A horrified Mr Bond immediately sent two of his youngest staff, aged 19, home, and called the police – but officers said they were powerless to act because it was a private event.

Mr Bond said: "To say I was shocked was an understatement. I was lost for words. It was as if a switch had been flicked on.

"The first thing we saw was one couple at it on a window sill. When the haze from the dry ice in the disco room cleared we realised it was going on everywhere. That's when the penny dropped that it was a swingers' party. The guests were all public school types and I jokingly said to one: 'I suppose you are a High Court judge'. He replied: 'You're not far off the mark'."

Mr Bond, a retired estate agent who bought the Grade I Listed Tudor house for £1.94 million in 2004, added: "I'm just taking it in good humour because it was supposed to be a private party."

Mike Voorvaart hailed the event – the company's first in England – a "great success", and said the lack of British prudishness was a revelation. He said: "I think Grahame was quite surprised by what happened, but he said we could come back if we tone it down a bit next time."