The existence of the cave at the former Italian prime minister’s Villa Certosa estate had been rumoured for years but the first photographs of it emerged on Friday.

They were obtained by Antonello Zappadu, an Italian photographer who made his name in 2009 by taking long-lens pictures of scantily-clad showgirls at Mr Berlusconi’s residence.

The cave, which could have come straight out of a James Bond film, features a swimming pool, its floor decorated with a mosaic of Poseidon, the god of the sea, holding a trident.

It is connected to a short tunnel and a gate which reportedly leads straight to the sea.

The cave is connected to the rest of the villa by stairs and a passageway, which are illuminated by discreetly placed lights set into the floor. . .