It's an accepted part of everyday life for people using public transport: you wait for a bus and then two come at once.

Or in this case, 13.

This was the sight greeting shoppers this morning when traffic came to a screeching halt.

Norman Kemp, owner of Nu-Venture Coaches LTD, said the jam was caused by a security vehicle left unattended in Mill Street and the ensuring chaos had left several of his drivers caught up.

He said: "There is no redundancy room on High Street if anything happens or traffic gets snarled up. One of our drivers said it took him 25 minutes to get out of it. It seems as if it would be an incident that is avoidable.