The Queen is celebrating her 96th birthday on Thursday in Sandringham.
Britain’s longest-reigning monarch travelled by helicopter to her Norfolk estate, where she is being joined by family and friends.
She is thought to be staying in a cottage particularly liked by her late husband, Prince Philip.
A photograph has been released to mark the birthday, showing the Queen with two ponies and reflecting her lifelong interest in horses.
The picture was taken at Windsor Castle, where the Queen now mostly stays, and shows her with two Fell ponies, who will appear in the forthcoming Royal Windsor Horse Show.
The Duke and Duchess of Cambridge wished the Queen happy birthday on Twitter, calling the monarch an “inspiration to so many across the UK, the Commonwealth and the world”, and sharing a photo of the Queen and Prince Philip with seven of their great-grandchildren.
Prince Harry suggested in a US TV interview that the Queen might be downplaying this latest milestone, saying that “after a certain age you get bored of birthdays”.
But she will be spending time at Wood Farm, a cottage described as “small and intimate” by former housekeeper Teresa Thompson, and a place with strong associations with Prince Philip, who died a little over a year ago.
The Queen was in Sandringham earlier this year when she marked her accession to the throne in 1952.
She was born in 1926, not in a royal residence, but in a London townhouse on Bruton Street, where she first lived with her father and mother, who became King George VI and Queen Elizabeth.
Birthday wishes have been sent by Prime Minister Boris Johnson and Labour leader Sir Keir Starmer and gun salutes were fired.
The prime minister also paid tribute to the monarch’s “dedicated and faultless service” in a pre-recorded address posted on Twitter.
The Queen’s Guard played Happy Birthday during the Changing of the Guard outside Buckingham Palace. (BBC)