The royal grandsons are teaming up to throw a giant street party in June

By Simon Perry
Updated September 11, 2015 04:35 PM

Queen Elizabeth may have just passed her biggest milestone yet in her own understated way, but Prince William and Prince Harry and their cousin Peter Phillips are not going to let the next one go off without a bang.

William and Harry are throwing their weight behind a massive street party, which will stretch the length of the famed outdoor avenue in London known as the Mall, to mark the Queen’s 90th birthday in the spring.

About 10,000 people are expected to attend the picnic lunch, which is being billed as the Mall’s “largest-ever street party,” along the half-mile long road in St. James’s Park leading to the gates of Buckingham Palace on June 12.

The “Patron’s Lunch” will celebrate the 600 charities and organizations that Elizabeth has supported during her record-breaking reign. The Queen and her husband of 68 years, Prince Philip, will be guests of honor at the party, which is the brainchild of their eldest grandchild Peter Phillips, who runs a company that will organize the event. William and Harry are joint presidents of The Patron’s Lunch.

The party will be the culmination of a weekend of festivities marking the Queen’s “official” birthday. (Her real birthday is April 21!) The celebrations begin with a “service of thanksgiving” at St. Paul s Cathedral on June 10, which is also Prince Philip’s 95th birthday. The Queen’s annual birthday parade, Trooping the Colour, takes place on June 11 and the street party is the next day.

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