Squatters shacked up in a grand building metres away from Buckingham Palace have been evicted in an early morning "stealth mode" operation.

Activists were branded a possible risk to the Queen's security for occupying the seven-storey property on Buckingham Gate, in the shadow of the monarch's residence.

Eviction efforts took place at around 4am on Saturday after the building's owners filed a submission to the High Court.

Daniel, one of the 30 campaigners who had been occupying the building for around four days, said more than 60 bailiffs executed the eviction.

The 37-year-old told the Press Association: "It was pretty unprecedented. To just wake up and you are surrounded by bailiffs, they came in in stealth mode.

"I opened my eyes to bailiffs on the staircase."

He described it as a "swift and silent eviction", adding: "I didn't see them (the bailiffs) turn on the lights until I was outside at the door."

With numerous evictions under his belt, having occupied properties for more than six years, Daniel said he had never seen one executed so quietly and with that number of bailiffs.

Quizzed on whether they will move into another property in the Buckingham Palace area, Daniel said: "We have to stay in the area... it would be nice to continue with it."

Warning signs stapled to the door of the once-lavish property, which neighbours the Swaziland High Commission, state the premises is now being protected by County Enforcement Group.

The company state on their website that they are civil enforcement agents and high court enforcement and specialise in a number of areas, including the "eviction of squatters".

Videos posted on a social media site by Occupy London shows the protesters leaving the building they had re-branded the Rogue Embassy.

Within some of the footage, a man can be heard describing how squatting 100 metres from Buckingham Palace was the "basic aim" of the protest.

Walking past the royal residence, another man added: "Bye bye Buckingham Palace, bye bye Queen. It's been an interesting experience for all of us, probably for her as well."

Daniel said their Rogue Embassy is "now on the move".

Court documents shown to the Press Association by the squatters cited a Metropolitan Police royal specialist protection officer who flagged a "potential security risk" posed by the group.

Concerns were raised that, if the occupiers accessed the adjoining roof, they could directly peer into the gardens of the royal grounds.

But one of the protesters insisted they were not "going to do anything".

Snipers stationed on the roof of Wellington Barracks were in "regular contact" with a next-door owner to raise concerns about the view into the palace gardens from the roof, the document said.

Security considerations were further fuelled by a post on the group's social media feed, which said they had decided to relocate "as close to the Queen's bedroom as possible", it added.

One organiser later claimed the message was just a joke.

It is the third high-profile building the band of squatters, who claim to be part of the Autonomous Nation of Anarchist Libertarians, have entered this year.

They were evicted from a multimillion-pound property in Eaton Square, central London, last month, before immediately moving into a nearby seven-storey building on Grosvenor Gardens.

Their latest home was festooned with banners before the eviction, including one which read: "Behind every great fortune lies a great crime."

Owned by Bahraini Abdulrahman Al Jasmi, it has stood derelict for decades, the group claimed, leading them to repurpose it as an embassy for "indigenous people" and "nations that are not recognised".