In the past my cousin was arrested in Bristol for being a graffiti artist.
Instead of just dishing out punishment he was allocated a wall of his own to
paint. This type of approach was very successful.

Maybe London Underground could allocate trains to the talented artists. One
other train could be markd out so the taggers could have a portion each for
thier signature.

Graffitti artist are very protective of thier work and would punish anyone
who dared to touch it.