In the UK, Bristol’s Banksy is a typical street artist – famous for his black and white stencils and irreverent humour. His rival, the late King Robbo, was a master of freehand graffiti who considered Bansky’s jokey stencils a bit of a soft option compared to his hardcore spraygun skills.

Street art is gently counter-cultural but doesn’t cock a snoot at Joe public.  In the digital age, a work can quickly spread by social media and bypass the old-school gallery system. To a street artist, the whole city is his showroom.  Artists encourage photographs to document their works – and are happy to see them reproduced as prints for the suburban home.

In the US, Shepard Fairey is one of the key founding figures in Street Art. This Los Angeles trained illustrator put hundreds of black and white posters and stickers of the stylized face of wrestler Andre the Giant all over the city. The meaning of these was elusive: a private joke that still has people intrigued. His stylized image of Barack Obama (above) became a defining icon of the presidential elections.