It stated that Her Majesty "greatly enjoyed" her birthday celebration and the flypast in London during the Trooping the Colour parade.
VIDEO: The Queen joins royal family on balcony for Jubilee celebrations
However, she did "experience some discomfort," due to which she will be pulling out of Friday's national thanksgiving service.
"Taking into account the journey and activity required to participate in tomorrow's National Service of Thanksgiving at St Paul's Cathedral, Her Majesty, with great reluctance, has concluded that she will not attend," the statement read.
It is also believed that the Queen experienced "episodic mobility issues," according to a royal source, although she will be attending the beacon lighting event on Thursday evening.
Working royals were invited to join the Queen on the balcony
On Thursday morning, the Queen led her family in marking her annual birthday parade – a military spectacle that involved more than 1,200 officers and soldiers and 240 horses from the Household Division putting on a display of pageantry. Hundreds of army musicians also added to the festivities as the colour was trooped by the 1st Battalion, Irish Guards.
Trooping the Colour is an exciting event in the royal diary, full of pomp and ceremony. The Queen was on fitting form as she attended her first wide-scale birthday event since the pandemic.
Thousands of royal fans descended on the Mall in central London to watch the parade and see the Queen and members of her family.
Thousands of people lined the Mall to watch the flypast
The monarch did appear in great spirits then, smiling at the crowds and taking the atmosphere in while also enjoying spending time with her grandchildren and great-grandchildren, who joined her on the balcony during the procession.
Like this story? Sign up to our special Queen’s Platinum Jubilee newsletter to get latest news, photos and videos related to Her Majesty's special milestone.