Gun salutes will ring out Thursday to mark Queen Elizabeth II's 96th birthday, although the monarch herself was expected to mark the occasion with little fanfare.
It has been a troubled year for Britain's royal family, with concerns over the queen's health and questions over the future of the monarchy.
Rounds will be fired from the Tower of London and Hyde Park in the British capital, where a military band will also play "Happy Birthday".
Royal tradition since the 18th century has also seen the monarch have a second, official birthday, typically celebrated in warmer weather in June.
This year's official birthday coincides with four days of public events from June 2 to 5 to mark the queen's record-breaking 70th year on the throne.
British media said the queen has flown by helicopter from her Windsor Castle home, west of London, to her Sandringham country estate in eastern England.
There, she is reported to be spending time at the cottage where her late husband Prince Philip lived after he retired from public life in 2017.
The Daily Mirror quoted an unnamed royal source who said the trip was being viewed as a "positive step" given the queen's recent health problems.
Since an unscheduled overnight stay in hospital last October, she has cut down massively on public appearances on doctor's orders.
A back complaint and difficulties standing and walking have seen her cancel a number of engagements, including recent church events to mark Easter.
A bout of Covid-19 in February left her "very tired and exhausted", she told doctors and patients at the Royal London Hospital during a virtual event earlier this month.
But her grandson Prince Harry told US broadcaster NBC in an interview aired on Wednesday that she was "on great form" when he saw her last week.
The queen was last seen in public at Westminster Abbey in central London on March 29 at a memorial service for Prince Philip, who died last year aged 99.
Health and succession
The queen's enforced retreat from public life in her Platinum Jubilee year has increased attention on the succession and the monarchy's future.
Her eldest son and heir, Prince Charles, has assumed more of his mother's responsibilities in preparation to take over the throne.
His popularity has increased in recent years, according to an Ipsos poll of more than 2,000 adults in Britain in March.
But his 43 percent approval rating is still well behind his mother (69 percent), his eldest son Prince William (64 percent) and his daughter-in-law Kate Middleton (60 percent).
Some 42 percent of those surveyed also said they believed Charles, 73, should step aside for William, who turns 40 in June.
Aside from questions about the queen's health and the succession, the royals have rarely been off the newspaper front pages due to a succession of scandals.
Last month there was controversy after the queen's disgraced second son Prince Andrew supported her at Prince Philip's memorial service.
In February, he settled a US civil claim for sexual assault that had earlier seen him stripped of his honorary royal military titles and charitable roles.
The palace is said to be bracing for fresh revelations about royal life from Harry, who is due to publish his memoirs later this year.
The former British Army captain quit the royal frontline last year and moved to California with his American wife Meghan Markle.
From there, the couple accused the royal family of racism, while Harry claimed his father Charles and brother William were "trapped" within the system of the British monarchy.
The future of the royal family's global reach is also far from assured.
The queen is head of state of Britain and 14 other Commonwealth countries around the world.
But Barbados became a republic last year and a number of other Caribbean countries, including Jamaica, have since indicated they want to follow suit.