Armed cops apprehended a Windsor Castle intruder reported to have been 'carrying a crossbow' on Christmas Day - as the Queen was preparing for mass.
A 'top-level emergency' threat was raised as Her Majesty was getting ready to greet sons Charles and Edward, Sunday Mirror reports.
A man reportedly breached perimeter security, but police he was seized before he could reach the building itself.
READ MORE: Intruder 'carrying weapon' arrested in grounds of Windsor Castle as Queen celebrates Christmas
A 19-year-old man was arrested.
Security sources confirmed to the Sunday Mirror that the man was allegedly carrying a crossbow when stopped by police.
One source told the paper: "Security controllers monitoring the CCTV couldn’t believe their eyes when they spotted the man carrying what appeared to be a crossbow and scrambled armed police to the scene immediately as a top-level emergency.
"A full-scale protection plan was executed to ensure the safety of the Queen, who was in her personal quarters.
"It was a really professional response from everyone, but it was hugely alarming to witness the intruder on the scene. There were real concerns the situation could have massively escalated having such a dangerous weapon to deal with.
"When word got out that he had been apprehended, everyone breathed a huge sigh of relief – but it’s obviously tremendously concerning."
The Queen was at Windsor for her first Christmas since her beloved husband Prince Philip died.
Plans for a traditional stay at Sandringham were abandoned because of Covid.
A royal source said: "It is obviously a worry to have to deal with a break-in like this, especially after Her Majesty has been through so much this year and in the lead-up to Christmas.
"There will have to be a major evaluation of the security procedures and protocols after this event.
"Fortunately the intruder was apprehended and police were on the scene almost immediately, but there is a chill in the air over what could have been."
Thames Valley’s Police and Crime Commissioner Matthew Barber said the force would be liaising with Scotland Yard – responsible for policing Windsor – as part of a joint probe.
He said: "Everybody will be naturally shocked to hear the news but I think the encouraging thing is that it seems the security measures were effective.
"This individual was arrested at the earliest opportunity and had not entered any buildings. I’ve spoken to the Chief Constable of Thames Valley Police and we want reassurances about the security."
The Queen was told of the security breach as she was preparing to greet Charles, 73, and the Duchess of Cornwall, 74, for the service at St George’s Chapel.
Prince Edward, 57, his wife Sophie, 56, and their children, Louise, 18, and James, 14, were also visiting Her Majesty.
A spokesman for Thames Valley Police said: "Officers responded to a security breach at around 8.30am within the grounds of Windsor Castle. A 19-year-old from Southampton has been arrested."
Supt Rebecca Mears added: “The man has been arrested on suspicion of breach or trespass of a protected site and possession of an offensive weapon.
"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."
