No-fly zone introduced above British Queen Elizabeth's Windsor Castle

Thames Valley Police force said the restrictions come into effect from January 27

Tourists in front of the Henry VIII gate at Windsor Castle on Christmas Day. AP

UK police on Tuesday said they were imposing a no-fly zone above Windsor Castle, one of Queen Elizabeth II's primary residences, after a security review.

The announcement came after a man, 19, was arrested for breaking into the castle grounds armed with a crossbow on Christmas Day, as the monarch was spending a low-key festive season at Windsor.

Thames Valley Police force said that effective from January 27, no aircraft can enter airspace up to 760 metres above the castle, within a radius of 2.3 kilometres without special permission.

"This order is an additional method to keep the community living near to this iconic location safe," the force said.

Windsor Castle is west of London, near Britain's busiest airport at Heathrow.

The Queen, 95, usually celebrates Christmas at her Sandringham estate in eastern England, but she remained at Windsor Castle this time after the trip was cancelled because of a surge in Omicron Covid infections.

Queen Elizabeth at the 2021 Trooping the Colour parade. The year has been one of loss and sorrow for the British monarch, capped by the cancelled plans for an extended family lunch to celebrate Christmas at Windsor Castle. All photos: Getty Images

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Queen Elizabeth attends the Qipco British Champions Day at Ascot Racecourse in October.

The British monarch on a screen via video link from Windsor Castle during a virtual audience at Buckingham Palace in October.

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Queen Elizabeth attends a military ceremony in the quadrangle of Windsor Castle to mark her official birthday in June.

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Prince Charles, Camilla, Duchess of Cornwall, Queen Elizabeth, Prince William, Duke of Cambridge, and Catherine, Duchess of Cambridge, arrive for a reception at The Eden Project during the G7 Summit in June.

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Queen Elizabeth watches pallbearers carry the coffin of her late husband, Prince Philip, the Duke of Edinburgh, into St George’s Chapel during the funeral at Windsor Castle in April.

Pallbearers with the coffin of Prince Philip at Windsor Castle in April.

Queen Elizabeth signs her annual Commonwealth Day Message in St George's Hall at Windsor Castle to mark Commonwealth Day in March.

The teenager was arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon. He was detained under the Mental Health Act.

Queen Elizabeth, already Britain's longest-reigning monarch, is due to celebrate her Platinum Jubilee this year to mark 70 years since her accession to the throne in 1952.

She was forced to cut back on public appearances after a health scare in October, in which she spent a night in hospital.