Prime Minister Theresa May has offered her congratulations to the Queen on her Sapphire Jubilee, hailing her as “ truly an inspiration to all of us”.
Mrs May said it was “a testament to her selfless devotion to the nation” that the Queen had made clear she did not want official celebrations to mark the historic milestone.
The prime minister said: “Today’s Sapphire Jubilee marks yet another remarkable milestone for our remarkable Queen.
“I know the nation will join with me today in celebrating and giving thanks for the lifetime of service Her Majesty the Queen has given to our country and to the Commonwealth.
“It is a testament to her selfless devotion to the nation that she is not marking becoming the first monarch to reign for 65 years with any special celebration but instead getting on with the job to which she has dedicated her life.
“She has truly been an inspiration to all of us and I am proud, on behalf of the nation, to offer our humble thanks and congratulations on celebrating this Sapphire Jubilee.”
Meanwhile, gun salutes rang out across London to commemorate the occasion.
The Queen acceded to the throne following the death of her father, George VI, on February 6 1952.
She spent the day privately at her Sandringham Estate in Norfolk, where the monarch spends her winter break.
But in London a 41-gun salute was fired by the King’s Troop Royal Horse Artillery in Green Park at noon.
The Band of the Royal Artillery played a selection of celebratory music close to the firing position, and 89 horses pulled the six First World War-era 13-pounder field guns into position in the park.
The Honourable Artillery Company fired volleys at the Tower of London to mark the Sapphire Jubilee of the Queen’s accession.
They fired a 62-round Royal Salute from Gun Wharf at 1pm – with an extra 21 volleys for the citizens of the City of London to show their loyalty to the monarch.