Writer's block - the art of Graffiti

Why would people in the property business become grafitti artists, and what is it that's so compulsive about spreading your tag, or trademark. in the same way that young kids defacing property very often write their own name in a quest to remain anonymous . It's not a new game, any ancient building has either been  gouged with the initials of bored bystanders or look behind the main facade and there will  be strange characters and creatures added by the original nameless craftsmen; any gnarled tree trunk seems to be asking for initials and hearts to be carved by the lovers who repose underneath them.
Last month Kristian Holmes, a respected property surveyor, was jailed for causing £250,000 of damage to trains, walls and bridges. However former train-writer Glynn Judd (tag name Noir) , who painted trains most nights while working as a property investor by day, reckons that many graffiti writers are upstanding members of the community. He also maintains that trains have a protective film on them and the paint used by taggers is water-based acrylic so doesn't take long  to clean, only ten minutes if the yards have a washer  system. A while back he gave up tagging, gave up working in the City, retrained and became a community project worker, painting the Dizzee Rascal house for the Olympics opening ceremony. But a higher profile and visits to galleries meant that the transport police squad caught up with him last October and he had a short spell in prison.
He says to stop criminal damage, you have to start with educating kids. But where to start, other than engaging kids in community projects of authorised 'murals' - or legal graffiti. What is it about graffiti that attracts - the danger of being out at night engaged in illegal activity, or the sheer scale and size of it? Judd says for him it was the speed of trains and maximum impact, the way what you've painted quickly goes from one side of the country to the other. So is it just another aspect of our celebrity culture, everyone wanting their moment of fame, their name in lights?
According to Judd, who is writing a book, 'Addicted to steel: the story of London's Most Wanted Graffiti Vandal',  modern graffiti originated in the late 1960s in Philadelphia; on the New York subway system in the 1970s; and by the mid 80s it had gone global. Certainly this is when stencils first appeared.
But there are all kinds of earlier examples, for instance Arthur Stace, the Eternity Man, who spent his nights writing Eternity in chalk all over Sydney for thirty-five years after his conversion to Christianity in 1930.
The most famous graffiti artist, Bristol-based Banksy, who it's said is an ex cathedral-school boy, has his work sold for large sums nowadays, while councils fight to keep his work in the community, and residents presumably feel anxious about the walls of their homes and businesses disappearing. He has a book of his work, 'Wall and Piece', and made a film in 2010  'Exit through the Gift Shop', with a puzzling look at his world and his rivals, which was nominated for the best documentary award.
Yesterday, 'No Ball Games' was the second Banksy sprayed on a London wall to be removed recently, probably for auction. Last month 'Slave Labour' was sold for £750,000 by the same company - watch this space.