NAMES changed to protect identities, this is the story of a man named Tox, who is facing a prison sentence for drawing on walls, and a man named Banksy, who has made a mint and enjoyed unprecedented adulation for, um, drawing on walls.

In fact, Banksy is now so renowned that his artwork of a rat in Clipstone Street, Fitzrovia, may have escaped the dreaded prospect of being whitewashed this week by gaining the protection of a Perspex screen.

But we’ll come to that later.

Tox, in contrast to his...