An intruder who broke into the grounds of Windsor Castle on Christmas Day carrying a crossbow has been sectioned under the Mental Health Act.

       The man from Southampton was arrested with the weapon after apparently using a rope ladder to scale a metal fence to enter the gardens at the Queen’s Berkshire residence.

       It is understood he was spotted on CCTV “within moments” triggering a team of armed response officers to arrest him at 8.30am, just hours before the Queen was due to celebrate Christmas with her family.

       In a statement issued last night, a Metropolitan Police spokesman said: “A 19-year-old man from Southampton was arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon.

       “Security processes were triggered within moments of the man entering the grounds and he did not enter any buildings.

       “Following a search of the man, a crossbow was recovered. The man was taken into custody and has undergone a mental health assessment - he has since been sectioned under the Mental Health Act and remains in the care of medical professionals.”

       The security breach is likely to lead to a review by police to establish what lessons can be learned from the incident.

       Dai Davies, a former royal protection officer, said one possible threat such an armed intruder could have posed was a crossbow bolt being fired at a windscreen and then hitting an occupant of one of the vehicles arriving at the Windsor chapel.

       “The security threat can often be at its highest when VIPs are going to or from a known location,” he said. “The bolt from a high-powered crossbow could possibly go through an armoured glass window - they can be very powerful weapons.”

       About an hour after the Christmas Day arrest, the Queen welcomed Prince Charles and Camilla to the castle. The Earl and Countess of Wessex along with their children, Lady Louise, 18, and Viscount Severn, 14, also attended a Christmas Matins service in Windsor Castle. The Duke and Duchess of Gloucester also visited the castle for the service at the private chapel.

       It has been widely publicised that the Queen, 95, was having Christmas at Windsor instead of Sandringham due to concerns over the spread of the new Covid variant.

       Mr Davies said although the security breach was tackled by police at the earliest possible moment, protocol dictates that a senior officer would conduct a thorough review to see what lessons can be learned.

       “The security operation went to plan,” Mr Davies continued. “I don’t think there were any failings in security at all. They reacted precisely as you would expect them to.”

       The police investigation is likely to consider how the suspect got from Southampton to Windsor so early on Christmas morning when rail and bus routes were suspended. It raises the prospect he could have driven up very early or arrived in the town on Christmas Eve and stayed overnight in a hotel or bed & breakfast.

       Muthu Kesavan, a Windsor businessman, said he saw some police activity shortly after the arrest on Christmas Day.

       "I was working and I saw the police cars driving around the castle at around 9am,” he said. “I imagine it happened around the back of the castle because it was all normal at the front gates.”

       Two weeks ago, a woman was arrested after she ran up to Prince Andrew’s car and banged on the window. The security breach happened as the Duke of York drove into the Windsor estate.

       In April, a 44-year-old woman who claimed to be engaged to Prince Andrew was let into his official Windsor residence by security guards.

       The smartly-dressed Spanish woman was said to have wandered around the grounds of his Grade II listed Royal Lodge in Great Windsor Park. She has since been sectioned under the 1984 Mental Health Act.