Tickets to a gala street party planned in the heart of London to mark Queen Elizabeth II's 90th birthday this year will open to the public to buy for 150 pounds each.
Peter Phillips, the monarch's grandson whose entertainment firm is organising the extravaganza, said the not-for-profit event on June 12 will be called "Patron's Lunch" and have a "carnival atmosphere".
"There's a huge amount of pride, the fact that I'm able to celebrate, to put something on, to put a celebration on which ultimately she appreciates, she enjoys and she thinks is a great idea," said Phillips,the son of the Queen's daughter, Princess Anne, who came up with the idea as director of Sports Entertainment Ltd.
"It's not exactly a cheap exercise. Fortunately our corporate partners have provided the funding for the majority of what we are budgeting," he added.
Most of the 10,000 guests will be from organisations associated with the Queen.
While a majority of the tickets have been pre-allocated, the firm will be able to sell 40 per cent of these through auctions or raffles, raising money to cover the cost of their other tickets or to go into charity funds.
A ballot will open to the public in February for a minimum of 1,000 tickets, and winners will then be able to buy tickets from the event's website.
All guests will be treated to a hamper-style lunch on a grand scale.
In total, the ticket sales will raise 1.5 million pounds towards the cost of the event, with any surplus donated to a new Patron's Fund to benefit various charities.
During the event, a carnival parade will travel through The Mall in central London to entertain the guests, and the Queen and Duke of Edinburgh will take to a stage to listen to speeches marking the occasion.
They will later join grandsons Prince William and Prince Harry, joint presidents of the event, in the royal box for part of the day.
Phillips said the Queen had heard about his plans before he had a chance to tell her and recalled how upon approaching her with the idea she said: "I've heard you're up to something."
The party will be the culmination of a weekend of UK-wide celebrations.
Other events taking place over the Queen's official birthday weekend will include a service of thanksgiving at St Paul's Cathedral and the traditional Trooping the Colour ceremony, also known as the Queen's Birthday Parade, at Horse Guards Parade in London.
The Patron's Lunch is intended to honour the Queen's lifetime service to the UK, as well as marking her patronage of more than 600 charities and organisations.
The Queen celebrates two birthdays each year: her actual birthday on April 21 and her official birthday on a Saturday in June.
