A man armed with a crossbow who was arrested after breaking into the grounds of Windsor Castle on Christmas Day has been detained under the Mental Health Act, police have said.

The 19-year-old from Southampton was arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon at about 8.30 yesterday morning after a security alert at the castle, where the Queen is in residence.

In a statement the Met Police said: “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.

“Following a search of the man, a crossbow was recovered.

“Inquiries into the full circumstances of this incident are being progressed by Metropolitan Police specialist operations.”

The Queen has been celebrating Christmas at Windsor this year after cancelling her traditional plans to go to Sandringham.

Superintendent Rebecca Mears said yesterday: “An investigation is ongoing following this incident and we are working with colleagues from the Metropolitan Police.

“The man has been arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon. He remains in custody at this time.

“We can confirm security processes were triggered within moments of the man entering the grounds and he did not enter any buildings.

“Members of the Royal Family have been informed about the incident.

“We do not believe there is a wider danger to the public.”

During her annual Christmas message yesterday, the Queen reflected on a year of personal grief in her moving annual Christmas Day message this afternoon.

She said there was “one familiar laugh missing” following the death of her husband Prince Philip amid the continuing impact of the coronavirus pandemic.