Thieves broke into the grounds of Windsor Castle and stole two vehicles from royal land, police said, in a major breach of security.

Police are investigating a security breach at the 16,000-acre Windsor Castle estate which serves as the primary residence for Prince William, Catherine, Princess of Wales and their three children after a robbery took place on the grounds in October.

The intruders entered a farm building on the castle estate last month and stole an Isuzu pickup and a quad bike, according to the local police.