Motorists were led on a mystery tour through Essex after a policeman accidentally switched on a sign telling the drivers behind to "Follow Me."
Five motorists took the instruction to heart and tailed the police Volvo for a number of miles as the officer carried out his routine patrol.
The officer - now dubbed the Pied Piper by colleagues - noticed the convoy near Maldon and pulled over.
Essex Police said the unnamed inspector had apologised to the motorists.
A police spokeswoman said the matrix system on top of the car is used to display instructions to drivers such as "Pull Over" or "Follow Me."
She said: "Naturally, the law-abiding drivers saw the message and did as they were asked.
"Some had followed the car for some time, but they were all very understanding when the officer explained the sign had been accidentally switched on."