I'll give you another clue. The car was tipped on end and the chassis was filled with the material by pouring it down the chassis legs.

Concrete?

Winner!

Indeed the car was owned by a notorious bodger who apparently swore by upending 2cvs and filling the chassis with concrete.

Bizarrely, the car was involved in a murder/suicide case and is fitted with dual controls for learner drivers.

Russell,
even more amazing it never dawned on him that adding 150 kg of ballast wouldn't stop a chassis folding, since concrete has negligible tensile strength...

ken

Yeah, that was my thought too, if anything I could see it speeding up a collapse. I quite admire it, not for any engineering achievements, but for probably spending more time and money lashing it up and making it worse than it wod have done to just repair it properly. It had a 'crinkle' style vent flap too. Magic.

Russell, I know I'm Welsh and a 2cv'er, but unusually I don't drink alcohol, so you've got out of that one

One of my Dad's favourite stories is of when he needed to repair the rotten bottom of a Mini Van rear door that he had in the 60's. He shuttered the bottom and poured concrete through a rust patch near the top of the door. It did list a bit but was otherwise ok until he decided to replace it with a door from a scrappies a year later. He asked my Grandad to hold the door whilst he undid the hinges and my Grandad only realised how heavy the door was when it landed squarely on his foot

That's a new one. I knew a recovery driver who'd fill his bullbar on his transit to stop the front end lifting when he overloaded the... Forgotten what you'd call it, the old style lifty bit on recovery trucks before they all switched to panel vans and towing wollies.

Wouldn't the concretes alkalinity have increased it's tendancy to rust?