A major security breach at Windsor Castle has led to a shake-up in protection measures during which a number of most trusted police guards moved on, leaving senior royals "concerned."

A 19-year-old man, who was armed with a crossbow, was arrested on Saturday morning on the grounds of Windsor Castle where Queen Elizabeth II was due to celebrate Christmas with a few family members later in the day. The Southampton native was charged with "breach or trespass of a protected site" and possession of an offensive weapon, and was later sectioned under the Mental Health Act following an assessment.

Meanwhile, a shocking footage obtained by The Sun, believed to be of the same man, showed him threatening to "assassinate the Queen in revenge for 1919 Amritsar massacre." Jaswant Singh Chail had uploaded the pre-recorded video to Snapchat at 8:06 am on Christmas Day, 24 minutes before the suspect was arrested by police at Windsor Castle.

"I'm sorry. I'm sorry for what I've done and what I will do. I will attempt to assassinate Elizabeth, Queen of the Royal Family. This is revenge for those who have died in the 1919 Jallianwala Bagh massacre. It is also revenge for those who have been killed, humiliated and discriminated on because of their race. I'm an Indian Sikh, a Sith. My name was Jaswant Singh Chail, my name is Darth Jones," the man was dressed in an outfit apparently inspired by Star Wars said in the video.

Sith may be a reference to the leading villains in the space opera, and Darth Jones a mix-up of the names of the character Darth Vader and James Earl Jones who voiced him.

Around 379 were killed and 1,200 were wounded when British Brigadier-General R. E. H. Dyer opened fire at Jallianwala Bagh in Amritsar, Punjab, where a large peaceful crowd had gathered to protest against the arrest of pro-Indian independence leaders Dr. Saifuddin Kitchlew and Dr. Satya Pal. India gained its independence from Britain 28 years after the tragedy.

Scotland Yard has said detectives are examine the footage to ascertain if it was recorded by the same intruder arrested from the Queen's Berkshire residence. Meanwhile, the police instigated a reorganisation of their security arrangements that saw the removal of some police bodyguards trusted by the royal family members.

According to a report in Mail Online, Prince William, Kate Middleton, and Duchess Camilla are among senior members of the royal family who have expressed "concern" about losing their most loyal and longstanding personal protection officers. The Queen has also reportedly privately expressed her "disquiet" over the changes.

A source said, "Protection officers occupy very unique positions with MRFs [members of the Royal Family]. They are with them 24 hours a day and it understandably takes a long time to build up a good relationship of confidence and trust. Several very well-liked and respected officers have been moved on from their roles, not through any fault of their own."

The insider added, "It's simply because of this desire to shake things up a bit, sometimes for the sake of it, it seems. Everyone is unhappy about it, not least some of the principals [royals]. There have been a lot of changes in personnel, they have lost people they liked and valued. Some have made clear that they are really quite upset about it."

Queen Elizabeth II
(FILES) In this file photo Britain's Queen Elizabeth II smiles as she attends day three of the Royal Ascot horse racing meet, in Ascot, west of London. Britain's Queen Elizabeth II and her family are "delighted" at the birth of a daughter to her grandson Prince Harry and Meghan Markle, Buckingham Palace said in a statement. Photo: AFP / Adrian DENNIS