(LONDON) — An intruder infiltrated the barracks housing the soldiers who protect Queen Elizabeth in Windsor, The Sun newspaper revealed Tuesday.

The man, who was posing as a priest, talked his way into the Victoria Barracks, situated just outside the confines of Windsor Castle. According to The Sun, the man, who has not been named, claimed to be a friend of the chaplain for the Cold Stream Guards — one of the regiments that protects the queen. Soldiers allowed him in without checking for any identification.

The UK’s Ministry of Defense issued a statement saying it’s taking the breach “extremely seriously,” adding “it will be thoroughly investigated as a matter of priority.”

The intrusion took place while the Queen was away at Sandringham. The imposter was reportedly entertained by officers, eating and drinking with them before being offered a bed for the night. The police were eventually called the following morning, April 27.

“We received a report of an intruder at Victoria Barracks in Sheet Street, Windsor, at 9.20am on Wednesday,” Thames Valley Police said in a statement. “Officers attended and removed the intruder from the barracks. No further action was required.”

According to The Sun, which quoted TalkTV sources, “The man was known to local police as having mental health issues.”

An anonymous source told the newspaper: “The guy turned up at the gate, said his name was Father Cruise and claimed to be a friend of the battalion’s Padre, the Rev. Matt Coles. He was invited in and offered something to eat.”

The source added: “It was only later when he started talking about how he had worked as an ejector-seat test pilot and had some organs replaced that the chaps started to get suspicious.”

The incident was not the first security breach in Windsor; a man was apprehended last year on the grounds of the castle with a crossbow, police said.

ABC News Royal Contributor Robert Jobson explained that it’s harder to protect the Queen at Windsor Castle than it is at Buckingham Palace.

“Buckingham palace is like the White House; it has a strong parameter with very stringent security protocols and Scotland Yard officers within the compound,” Jobson said. “But Windsor Castle is more difficult to protect — it’s open to the public and it’s a vast area with many different entrances.”

Jobson added, “But it’s important to note that in this instance the castle grounds weren’t penetrated. That said if this had been a serious terrorist intent on causing mayhem the consequences could have been catastrophic.”

An increase in security ahead of the Queen’s Platinum Jubilee celebrations in June is therefore likely as a result of this incident, according to Jobson.

The UK will celebrate Queen Elizabeth’s 70 years on the throne with a holiday weekend in June. There will be a special Trooping of the Colour, a thanksgiving service at St. Paul’s cathedral and a concert at the palace. The finale to the four days of celebration will be a pageant through the streets of London.

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