I had a car parked outside my house for 6 weeks, it had been abandoned by occupants of house next door who had seemingly left the car when they moved out. it had no tax or nct and was on a public road. rang the guards, they told me they'd contact the Local Authority and report it. After 3 weeks of hearing nothing and the car still there, I rang the LA and hey presto the car was gone 1 week later, after it seemed they sent a letter to the owner (they had put a letter under the windscreen wipers, which I presume they sent a copy of to the owner). I know that this one was slightly different because it was a public road so thats why the LA got involved, but the guards should be able to remove a car if its not got the proper documentation on it. they should be able to trace the car back to the owner by the reg. no.