Alex Mitchell, 31, said: “I only saw the driver. I didn’t know what was going on or whether I should call the police.
“He pretended like he had broken down but he was there for at least two hours.”
Mr Mitchell said at one point the man came in and bought two Ribenas.
He said a piece of cardboard was left “gaffa taped to the wall” and when he returned the next day, the same person was there again.
“I asked him ‘who is the artist’ and he just winked at me,” he said.
“I’m not going to say whether it is Banksy or not, it definitely looks like one but no-one saw who painted it.”
“Maybe he was just passing through.”
Banksy does it with style again and again.