Two men scaled the fence of Windsor Castle after trying to break through a security gate as Prince William and his family were sleeping in a nearby cottage.
The masked thieves went on to steal farm vehicles from Shaw Farm, a working farm on the sprawling Royal estate, before they crashed into a security gate while fleeing.
It comes after it was revealed armed police were removed from the castles two public entrances.
The source told The Sun: It was a Sunday night on a school week so the young princes and princess would have been tucked in bed at Adelaide Cottage, just around the corner but still in the grounds.
There are alarms at Windsor Castle but the first time anyone knew there was a break-in was when they crashed through the security barrier at Shaw Farm Gate exit, they added.
The barrier has needed to be replaced as it was so badly damaged.
Prince William and Princess Kate live in a nearby cottage (Picture: AP)Prince William and Princess Kate live in Adelaide Cottage, which is on Windsor Estate.
A spokesperson for Thames Valley Police said in a statement: At around 11.45pm on Sunday October 13, we received a report of burglary at a property on Crown Estate land near to the A308 in Windsor.
Offenders entered a farm building and made off with a black Isuzu pick-up and a red quad bike. They then made off towards the Old Windsor/Datchet area. No arrests have been made at this stage and an investigation is ongoing.
Windsor Castle has had previous security breaches, including a crossbow-wielding intruder who stormed the castle in a plot to kill Queen Elizabeth.
Star Wars fan Jaswant Singh Chail wore a ‘Sith’ mask when he climbed into the grounds with a nylon rope ladder on Christmas Day 2021.
In 2023, Metro revealed a dossier of declassified files which showed a large number of security scares at the Royal residence, dating back to the 1960s.
The Prince and Princess of Wales live in Adelaide Cottage, on Windsor Estate (Picture: Shutterstock)On March 21, 1967, a ‘mental patient’ was found wandering in Engine Court having followed an employee through the Advance Gate at Windsor at around 8am.
Though it didnt happen at Windsor, one of the most notorious Royal security incidents took place in July 1982.
Michael Fagan scaled up a drainpipe at the palace before making his way into the Queen’s bedroom. He spent about 10 minutes talking to her about his family before being tackled by a duty footman.
Get in touch with our news team by emailing us at webnews@metro.co.uk.
For more stories like this, check our news page.