When do you check your petrol cap is on securely? On your drive? At the garage? Or in the fast lane of the A2?

This puzzling passenger chose the latter option, leaning out of the car's rear window to fiddle with the fuel cap as cars and lorries whizzed past near Bluewater.

Perhaps he's planning to fill up mid-drive, shaving literally minutes off the journey time and avoiding service station food into the bargain.

The video was captured on the dashcam of driving instructor Geoff Watkins, who said the explanation was a bit more mundane.

He told KentOnline: "The flap was open and the fuel cap appeared to be hanging loose, and banging on the side of the car.

"The passenger leaned out from the waist up to try to reattach it.

"It's clear the road safety message hasn't got through to everybody."

"If you have forgotten to attach the fuel cap, it's best to find somewhere safe to pull over, not try to do it in the fast lane of he A2."

Watch: Probably not the best place to do this

While Geoff made it clear the traffic had slowed, he estimated the car to be travelling about 25mph.

"It's not a safe thing to do - there's always the chance of getting run over by the vehicle behind if he fell out," he said.

While the petrol cap fiddler seems to have got away with it this time, let's just hope he doesn't decide to check the tyre pressure.