A new work understood to be by the street artist Banksy at the Royal Courts of Justice in London has already been covered up.

The artwork, which is on an external wall of the Queen’s Building, part of the Royal Courts of Justice complex, has been concealed by large sheets of black plastic and two metal barriers.

Photos on social media, purportedly of the new artwork, show a judge attacking a protester with a gavel.

The piece has not yet been claimed by Banksy but it is understood to be the latest creation of the artist, whose identity is the source of constant speculation.

The artwork is being guarded by security officials outside the building and sits under a CCTV camera.

Last summer, Banksy made headlines with his animal-themed collection in the capital, which concluded with a gorilla appearing to lift up a shutter on the entrance to London Zoo.

Other notable works included piranhas swimming on a police sentry box in the City of London, turning the box into what looked like a giant fish tank, and a howling wolf on a satellite dish, which was taken off the roof of a shop in Peckham, south London, less than an hour after it was unveiled.

The animals collection was made up of nine works including a rhino seemingly mounting a silver Nissan Micra, two elephant silhouettes with their trunks stretched out towards each other and three monkeys that looked as though they were swinging on a bridge.