Squatter Fernando explains the trick: “We arrived last Friday. We came from an unsecured window from behind this house, and we just came in here one day.”

It is unclear whether the squatters found the unsecured window already broken, or broke it themselves.

There are currently four people living in a seven-storey, 19-room mansion. More people are coming, the squatters say.

The UK has highly complex laws on squatting. A section of the Criminal Law Act of 1977 actually protects the occupants of a property, regardless of whether they own it. The police can only move in if the squatters damage or steal something.

A spokesman for the squatter group, Mark Guard, who claims he is producing a documentary on the squatters, says they are highlighting an important social issue.

Filmmaker Guard equates humans with natural disasters, saying “The properties usually are left empty by very wealthy people and that causes problems for the neighbors by attracting rats and pigeons and squatters, so they are squatting in them to highlight the problem of leaving this building empty.”

The squatters believe this house also belongs to the former Mrs Abramovich, given to her as part of her divorce settlement from the Russian magnate. But Mr Abramovich has denied having anything to do with the property, despite reports that he bought four houses on the square a few years ago, intending to convert them into one.

This is not the first time this group of squatters has targeted a multi-million dollar house in this area. Until last week, they were living a stone’s throw away from former Prime Minister Baroness Margaret Thatcher. And whoever actually owns this newly-squatted property will now have to get involved in a potentially lengthy legal battle to reclaim it.