The Queen’s official birthday is being marked with the annual Trooping the Colour parade.
She is being joined by members of her family and thousands of spectators to watch the display in Horse Guards Parade in Whitehall.
The Prince of Wales, the Duchess of Cornwall, the Duke and Duchess of Cambridge and the Duke and Duchess of Sussex are all attending.
The Queen celebrated her 93rd birthday in April.
The royal colonels – the Prince of Wales, colonel of the Welsh Guards, the Princess Royal, colonel of the Blues and Royals, the Duke of Cambridge, colonel of the Irish Guards and the Duke of York, colonel of the Grenadier Guards – are all riding on horseback as part of the parade.
The Duchess of Sussex made her first appearance in public since giving birth to her son Archie four weeks ago.
The Duke of Edinburgh, who celebrates his 98th birthday on Monday, has retired from official public duties and is not attending.
The Queen will watch the ceremony – which will this year parade the flag from the 1st Battalion Grenadier Guards – from a dais in Horse Guards Parade and she will also inspect the lines of guardsmen.
Following the parade, which involves around 1,400 soldiers, the King’s Troop Royal Horse Artillery will fire a 41-gun salute in Green Park.
The Royal Family will then head back to Buckingham Palace and gather on the balcony to watch the RAF flypast.
More than 20 aircraft will take part including modern jets and historic aircraft, with the Red Arrows as the finale.
Trooping the Colour originated from traditional preparations for battle and has commemorated the birthday of the sovereign for more than 250 years.