Once a guerrilla artist, Banksy is now almost part of the art establishment, with his graffiti work fetching tens of thousands of pounds at auction.
But that didn't stop railway bureaucrats ordering the removal of one of his pieces near Waterloo station.
Network Rail has now issued all its maintenance crews with a handbook of photographs showing examples of the work of graffiti artist Banksy, after one of his pieces of work, showing a monkey about to blow up a bunch of bananas, was painted over near Waterloo Station during a clean-up campaign.
The piece could have been worth thousands of pounds but the job was so thorough the only part of the image still visible is a faint trace of orange wire from the monkey's detonator.
The doors, in the Leake Street underpass beneath the lines into the Waterloo terminal, are now a sickly shade of magnolia and have since been covered in unintelligible graffiti tags.
A Network Rail spokesman admitted the organisation's staff painted over the creation.
"We don't want graffiti on our property and we will remove it," he said. "It's ugly, illegal and the public don't like it."
Many locals beg to differ. Adam Powell, who co-owns the Crockatt & Powell bookshop in Lower Cut, said: "I think it's a great shame that these graffiti paintings are being removed. It's corporate vandalism. They are a nice surprise when you come across them around London. As it happens, they've painted over the monkey really badly. The new coat of paint doesn't even come down to the bottom of the door."