The unnamed Mechanic worked for "Pinkerton's Auto Centre" and was called out by Bill Webster after the car he'd borrowed from a friend had developed a puncture on a country lane when he, Audrey Roberts, Janice Battersby and Roger Stiles were returning home from a booze-cruise trip to France. The key to unlock the wheel nut being nowhere to be found.
The mechanic had tools back at his workshop, stated that the job would take around a couple of hours and kindly offered the foursome a lift to a nearby service station, whereby he'd drop the car back off once repaired. Everyone was still in high spirits and drank cans of lager - except for Audrey who was disappointed that Bill had stooped to Roger and Janice's level.
As promised, the mechanic delivered the car back to the group, with Bill announcing that the invoice he'd received for the repair work amounted to "highway robbery".