Provenance and authenticity are always problems for art investors. How do you know it’s the real thing? So much more of a problem when the work of art or otherwise is a stencil on a wall that appears overnight. Banksy has posed a difficulty to collectors – even if it’s real, who owns that wall, and can I please take a chunk of it away? It has happened. These days you look for a Perspex covering to tell you if it’s just some schmuck graffiti-ing the wall or a Banksy worth it’s weight in gold bricks. Excitement followed by despair modulated by an upbeat local story then for North-West Londoners who found in Primrose Hill, Belsize Park and Kentish Town a series of grannies clasping kettles to their comfy bosoms next to the words: ‘Make tea not war’. A most suitable image for the leafier parts of Camden.

This one in Belsize Park comes complete with a Perspex covering. Surely a Banksy? The Camden New Journal quivered with excitement. But it was actually Mrs Beechey, who used to run that nice hardware shop in Regent’s Park Road. An unknown graffiti artist (Banksy declared the work not his – odd for someone who seemed to want to mix up the art market) was paying homage to the shop when it closed down. Mystery sort of solved, and Mrs B. tickled pink, but what about the uncanny Onion piece in June? Could it be a double bluff? Mrs Beechey is Banksy? Or a triple bluff: Banksy has been running that hardware store all these decades fronting for Mrs Beechey while she raced round the country spraying stencils.

Almost as exciting is the idea of Camden Council getting to grips with what is and isn’t good art on walls, now that some of them are worth a packet, by setting up a committee to make a team judgment on each new tag. Will there be a right of appeal by the artists who are turned down in the process? At least we will now have somewhere to go when we just don’t know if a picture is a work of art or an excrescence.