Volodymyr ­Zelensky is set to visit King Charles, a trip believed to be of “huge interest to Russian spies” – and there are three air forces near Sandringham Palace

King Charles meets Ukrainian President Volodymyr Zelensky at the Sandringham Estate(Image: PA)

Mystery continues to shroud the sighting of drones above Sandringham Palace – days before Volodymyr ­Zelensky visited the UK.

The drones were spotted last month before the Ukrainian leader’s last visit and, since three air forces near Sandringham Palace appeared to have been targeted by drones and mysterious lights six months ago, fears of World War Three have escalated.

A drone no-fly zone has now been imposed over the royal residence as concerns of “public safety and security” have been raised. The order has been passed for “security for members of the Royal Family and other dignitaries staying at or visiting Sandringham House”. Mr Zelensky, aged 47, stayed with King Charles on the 60-acre estate in March although the visit had been kept under wraps.

One of the drones spotted hours before he flew in was traced to a man sitting in a car nearby, who was not a member of the media. A source said: “It prompted a security scare. The operator was tracked down and spoken to.”

King Charles and Queen Camilla pictured at Durham Cathedral today(Image: PA)

Another drone was understood to have been traced to a photographer, but the source of others was still believed to be unknown. The source told The Sun: “There were several drones over Sandringham and not all were accounted for.

“Days later the total all-year round drone ban was imposed. There have been mysterious and unexplained drone sightings at three US air bases in East Anglia where Russia has been suspected. Zelensky visiting Charles would be of huge interest to Russian spies.”

While there was no specific UK threat, it is understood there was a concern that Sandringham is increasingly a location for imp­ortant State events. Drones and suicide aerial devices have been used to devastating effect in Russia’s war with Ukraine, which shows no signs of stopping. Modern technology means an explosive device or surveillance cameras can be operated from miles away.

Just 24 hours after Charles’s meeting with Mr Zelensky, the King hosted the then-outgoing Canadian Prime Minister Justin Trudeau last month. The monarch also met officers from the Canadian parliament, offering them “warm greetings” – in French.

A previous drone ban at Sandringham ran for only three months over winter and ended the day before Zelensky arrived. The new order was signed off by Transport Secretary Heidi Alexander, according to The Sun.

It states: “The Secretary of State has decided that it is necessary in the public interest to restrict flying in the vicinity of Sandringham House, Norfolk, having regard to the security considerations associated with this location by reason of it being the residence of members of the Royal Family.”