Two men are said to have scaled a six-foot fence and stolen a pick-up truck and quad bike from the grounds.

Windsor Castle’s security was breached last month, as masked men broke into the royal grounds while Prince William, Princess Kate and their children slept nearby.

Two men are reported to have scaled a six-foot fence and stolen two farm vehicles from a barn on a farm within the grounds.

King Charles and Queen Camilla were not staying in their residence at the time. However, the Prince and Princess of Wales and their three children, George, Charlotte, and Louis, were believed to be asleep in Adelaide Cottage.

A source told The Sun: “They must have been watching Windsor Castle for a while”. Adelaide Cottage is just five minutes from Windsor Castle, and the family is regularly seen using the wrecked gate, which is the nearest exit to their home.

Princess Kate and Prince William during Southport visit following the knife attack there (Image: Getty)

An officer stands guard at the Shaw Farm Gate, close to where theft occurred (Image: W8media)

The vehicles were stolen from Shaw Farm, which is a working farm within the Castle estate.

A source told the outlet: “They would have to have known the vehicles were stored there before they broke in and known when was the best time to get and escape without being caught.

“So they must have been watching Windsor Castle for a while.

“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. The barrier has needed to be replaced as it was so badly damaged.

The source noted that the incident occured on a Sunday night during a “school week”, meaning the young princes and princess would have been asleep in bed, minutes from where the incident took place.

An aerial shot of Windsor Castle (Image: Getty)

A vehicle leaves via the Shaw Farm Gate (Image: W8media)

A spokesman for Thames Valley Police confirmed the incident: “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.”

A spokesman for the Prince and Princess of Wales declined to comment