A total of four days of celebrations are kicking off today (2 June) with Trooping the Colour, the military parade that marks the Queen's official birthday.
Platinum Jubilee crowds were treated to the sight of the Duke and Duchess of Cambridge's children taking part in their first carriage procession as historic celebrations marking the Queen's 70-year reign began.
Cheers went up from thousands of spectators on The Mall as they caught sight of Prince George, Princess Charlotte and Prince Louis with proud parent Kate and the Duchess of Cornwall.
The nation is embracing the special extended bank holiday weekend of pomp, pageantry and star-studded festivities, which will see celebrities and the public gather in their millions in tribute to the monarch.
Here are some of the photo highlights from today's ceremony.
1.
Queen Elizabeth II watches from the balcony during the Trooping the Colour ceremony at Horse Guards Parade.
2.
Crowds near Trafalgar Square ahead of the Trooping the Colour ceremony at Horse Guards Parade, central London, as the Queen celebrates her official birthday, on day one of the Platinum Jubilee celebrations.
3.
Prime Minister Boris Johnson poses for a photograph with military personnel outside 10 Downing Street, London.
4.
The Royal Procession leaves Buckingham Palace for the Trooping the Colour ceremony at Horse Guards Parade, central London.