Was Walter Kershaw “Britain’s first graffiti artist”?

Oversized pansies painted on a wall with people standing in front of it
Pansies by Walter Kershaw

This question gets some coverage on the Guardian in this article about the Rochdale-born artist who rubbed councils up the wrong way in creating his artworks in the North of England. You can learn more about the man and his work, including various global assignments, on the Walter Kershaw website [Link expired]. There is also a radio documentary from the BBC.