Having graffitied buses, trains, walls and bridges throughout the UK and in France, Daniel 'Tox' Halpin has become notorious, appearing in TV documentaries and magazines and even earning the title "king of taggers".
But after a recent hearing, in which his artistic merit was debated, the graffiti artist's efforts were considered to be vandalism and he was convicted of criminal damage.
His arrest, along with four other men, is part of a crackdown called Operation Misfit by British Transport Police.
Detective Constable Will Livings, of the BTP, said: "Some people consider graffiti to be art but in reality it is nothing more than selfish vandalism that not only scars the railway environment but contributes to fear of crime and costs operators thousands of pounds in equipment downtime, as well as cleaning."
Halpin, 26, has repeatedly tagged the London Underground over the years. One manager said: "I don't know where you can't see a Tox tag: they are in places even I don't know how to access."
During Halpin's trial, the prosecution argued that his ubiquitous tag was not art. They brought ex-graffiti artist Ben 'Eine' Flynn as an expert witness to give evidence. He claimed that the Tox tags were "incredibly basic" and lacked "skill, flair or unique style".
The prosecutor Hugo Lodge said: "He is no Banksy. He doesn't have the artistic skills, so he has to get his tag up as much as possible."
In his defence, Halpin claimed that he had "retired" from writing Tox in 2005, by which time he had already received several asbos and community service orders.
He maintained that any newer Tox tags were the work of imitators. But recent CCTV footage showing Halpin in the act proved otherwise.
Prosecutor Lodge said: "Every time he talks about being Tox, his face lights up. He can't help but smile. He hasn't retired. He has turned professional. To maintain this, he has to keep getting his tag up. It's everywhere, and it's him."
Daniel Halpin was found guilty of seven counts of criminal damage.
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