A 19-year-old man who was arrested at Windsor Castle allegedly armed with a crossbow has been sectioned under the Mental Health Act.
It comes as police stepped up security at the Queen's residence after the apparent break-in attempt early on Christmas Day.
The man, from Southampton, was arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon, police said.
Officers decided to section him under the Mental Health Act following an assessment and he remains in the care of medical professionals.
Armed officers stood on guard and a surveillance vehicle was spotted on castle grounds this morning as police stepped up security for the Royal Family after the scare yesterday.
Sources suggested the man was armed with a crossbow and used a rope ladder to scale a metal fence but police refused to divulge exactly what he was carrying.
It is understood he was spotted on CCTV roaming the gardens at around 8.30am after scaling an outer wall and later triggered an alarm. Armed response teams raced to the scene within minutes.
It is not clear if the intruder got close to the Queen's private apartments. Police confirmed he did not enter any buildings and quickly ruled out any terrorist motive.
Police officers stands guard outside Windsor Castle after an intruder broke into the grounds
Heightened security inside the grounds of Windsor Castle this morning after a intruder broke into the grounds on Christmas Day
A police officer stands outside Windsor Castle after an intruder got into the grounds
Last night, a 19-year-old man from Southampton was being held on suspicion of 'breach or trespass of a protected site' and possession of an offensive weapon.
Crossbows are often referred to as 'lethal but legal' because they require no licence or registration and can be bought on the internet.
Within an hour of the security scare, the Queen, who is having Christmas at Windsor instead of Sandringham due to Covid fears, welcomed Prince Charles and Camilla to the castle.
Prince Edward and Sophie arrived soon afterwards with their children, Lady Louise, 18, and Viscount Severn, 14.
Charles, Edward and their wives were later photographed as they made their way to a service in St George's Chapel in the grounds of the castle.
The Queen missed the service in what is understood to be a personal choice. All the Royals then had lunch together.
Tourist stand in front of the Henry VII gate and take pictures at Windsor castle at Windsor, England on Christmas Day
The Prince of Wales and the Duchess of Cornwall, the Earl and Countess of Wessex and the Duke and Duchess of Gloucester have arrived for the Christmas Matins service in Windsor Castle
The Queen paid an emotional tribute to her late husband Prince Philip in her Christmas message, while sitting beside a framed picture of the royal couple (pictured)
The break-in came as the 95-year-old Monarch
