Our longer term aim is to disrupt them so that it all becomes too much hassle and they express themselves in a lawful way

Detective Inspector Paul Anstee

Police have also found photographs taken by artists themselves at the scene of their "artwork".

Detective Inspector Paul Anstee said: "It would be over-optimistic to think that we will find a graffiti den in every offenders room that we visit.

"However, who has ever heard of a graffiti criminal fearing that the police were going to come through their door with a warrant at any moment?"

'Reflected glory'

DI Anstee called graffiti a "blight" on people living in neighbourhoods affected by it and said there was a high level of public support for action to tackle the problem.

He said: "Our understanding is that tagging is an art form in the mind of the creator and that no self-respecting 'artist' is going to leave their insignia around the town for all to see unless it is something to be proud of - accordingly, practice makes perfect.

"Secondly, tag artists like to reflect in their glory and there is even a website where they are doing this."

Potential victims of the graffiti artists are being encouraged to make property less vulnerable by fitting metal lattice shutters and improved lighting.

Barnet Council is also supporting a code of conduct calling on traders to stop selling aerosol spray cans to youngsters.