Truck double-parked with engine running; driver was out of the vehicle on the phone and speaking with others

Clearly the truck was double-parked in front of #12 Upper Montagu Street to deliver some copper piping for this house, which is being renovated. When I politely asked the driver to turn off his engine, he said he wouldn't and that he was just leaving. It did not appear that the driver was just leaving because he did not head back to the truck's cabin and there was an order of new pipes to be unloaded. I think I heard the truck leave around 15-20 minutes later.