The Queen is marking the 68th anniversary of her accession to the throne.
Soldiers from the King’s Troop Royal Horse Artillery rode from London’s Wellington Barracks past Buckingham Palace to nearby Green Park for a Gun salute to mark the occasion.
Seventy-one horses pulled six First World War-era 13-pounder field guns to the north of the park where the 41-gun salute was fired.
The bells of Westminster Abbey, the gothic church where the Queen was married and crowned, will also ring out to mark Accession Day.
The celebration comes after a turbulent time for the monarch in recent weeks, with the Duke and Duchess of Sussex preparing to quit royal life.
Meanwhile the Queen’s second son, the Duke of York, is facing calls to speak to the FBI in the US.
Andrew, who turns 60 later this month, stepped down from royal duties in November after his disastrous Newsnight interview about his friendship with convicted sex offender Jeffrey Epstein.
The Queen – the nation’s longest reigning monarch – will mark the anniversary of her accession privately at Sandringham, where she has been staying during her winter break.
Elizabeth II has ruled for 24,837 days, passing her Silver, Golden, Diamond and Sapphire Jubilees and is just two years away from celebrating her Platinum Jubilee – 70 years on the throne.
She became the nation’s longest reigning monarch in September 2015, after overtaking her ancestor Queen Victoria.
The Queen was out and about on Wednesday – the day before her accession anniversary – opening Wolferton’s new pumping station, which dries out the surrounding marshland for farming on the Norfolk estate.
The Queen carried out the engagement 72 years after her father, King George VI, opened the original station in February 1948, and recalled how he used to walk his corgis there.
She also visited nearby RAF Marham on Monday to see training demonstrations of engine maintenance and weapons loading at the military base.
A fortnight ago, the Queen, 93, missed a planned meeting at her local Women’s Institute because of a slight cold.
The Duke of Edinburgh, 98, who spends much of his time on the Sandringham estate after retiring in 2017, spent four nights in hospital just before Christmas for treatment relating to a “pre-existing condition”.
Princess Elizabeth became Queen on February 6 1952, on the death of her beloved father.
She was just 25-years-old and thousands of miles from home on a Commonwealth tour with Philip in Kenya when the King died in his sleep from lung cancer at Sandringham House.
The Queen usually returns to London soon after the anniversary of her father's death.
She will be hosting a state visit by the Emperor of Japan at Windsor Castle in the spring.
Her granddaughter, Princess Beatrice, Andrew’s eldest daughter, is also preparing to marry property tycoon Edoardo Mapelli Mozzi later this year.