CAR WITH 4 OCCUPANTS BURNS IN 3 MNUTES SHORTLY AFTER GARAGE 'FIXED' IT!

On the way home from Sussex, a friend and I saw a Peugeot 2008 go from a smoking (but moving) car to a towering inferno inside 3 minutes. There were four occupants inside the car; two adults, two children. Crucially, nobody was hurt and the important things (school bag, scooter, helmet and phone) were rescued.
We tried to help but the front of the bonnet was too hot to open. The fire extinguisher didn't extinguish anything. Very, very quickly the car was engulfed in flame and beyond help.
I have never seen a car go from looking perfectly fine to being absolutely ruined by fire. The speed with which the fire took hold was alarming. Had this happened in a built up area, a school carpark, a drive-through or multistorey carpark, consequences could have been dire. As it was, nothing but a car and a patch of tarmac were damaged.
The most worrying aspect of this unfortunate fire is that the car had just been collected from the garage. It was sent there as it was losing power and smelling of petrol!
We only went to collect some wine and old barrels for a wedding...