The anonymous street artist Banksy caused a stir on Monday with a striking new work depicting a judge attacking a protester with a gavel, painted on one of Britain’s most prestigious court buildings. The image, in black and white, apart from a splatter of red on the demonstrator’s sign, appeared on an outer wall of the Royal Courts of Justice, an imposing London complex that houses the High Court and Court of Appeal of England and Wales and is considered one of the most secure locations in Britain. Now, just two days later, Banksy’s latest work is gone. The complex had quickly moved to block the artwork from public view, moving large metal screens in front of it on Monday. Then, on Wednesday morning, visitors to the mural filmed a man, wearing a mask, scrubbing the image off the walls, with two police officers standing guard nearby.