The Queen will celebrate her 90th birthday with a gigantic street party along The Mall for 10,000 attendees.
More than 600 charities and organisations will help plan the event, which will be held on Sunday 12 June 2016, and will see the road outside Buckingham Palace lined with streams of tables and chairs decked out in royal regalia.
A special service will be held at St Paul's Cathedral on 10 June and the party will be followed by the traditional Trooping the Colour ceremony at nearby Horse Guards Parade.
Members of the public will be allowed to join in the celebrations from the adjacent Green Park and Regents Park and Prince Philip, Prince William and Prince Harry will attend the main party.
By the time she marks the birthday, the Queen would have overtaken Queen Victoria's record as the country's longest serving monarch – she reaches that milestone on 3 September – after 64 years of service.
Grandson and organiser Peter Phillips, 13th in line to the throne, said plans were closely guarded but that the Queen was "excited" by the prospect.
"We want to reflect the service she's given to all her organisations and charities," he told the BBC.
"She's obviously been kept abreast through her office about all the developments, and the times I've had the chance to talk to her she's been excited by it."