Engine damage during Diesel Emissions testing

A few years ago, it was in the era when Coke tins had detachable ring-pulls, I had to test a similar scenario; I had no choice, a customer took me to court!
Let me go back. We diagnosed a blown head gasket/s on an old Peugeot V6 'euro-rattler' and proceeded to remove the 'heads. When the second of two bolts snapped, undoing, we stopped, and then destroyed our very best stud extractors. We next called out a specialist engineer who 'surrendered' to this hateful, stubborn peice of French poo. The engine was declared 'scrap' (I know, it was scrap when it came off the production line) and the customer was rung.
Time went by and the forms arrived. I decided to risk it in court, I had done nothing wrong, and I didn't feel inclined to 'roll-over' for the price of a new engine. Or car.
If the judge (registrar as they called them in those days) found in favour of the plaintiff, I was gonna be in for a big ££££ hit, including a CCJ, not good!
The customer claimed we had been 'negligent'. I had to show, beyond all reasonable doubt, to a man (we'll call him Judge) who had no idea what happens when steel bolts, ally heads 'n block and coolant that is rust coloured, all combine. In fact he took on a distinctly glazed appearance; I was losing him, not good!
"The plaintiff claims you were negligent in repairing his car and it will cost £x to put it right, what do you say"
Thinking quickly, I said...
"Sir, we were undoing the bolts when they broke, not tightening them, how could we have been negligent?"
I continued with the best example I could think of.
"Have you ever tried to open a tin of pop to find the ring-pull comes away on your finger but the can remains firmly closed, well it was like that, Sir"
It was amazing to see his face, he knew exactly what I meant and agreed that it HAD happend to him. Phew!
He sympathised with plaintiff and defendant alike, and we won.

In reality, no one won anything. Costs were not even awarded and we towed the rolling-chassis and boot full of bits back to the owners house.

What I am saying is, you may not be responsible for a vehicle when it falls apart during testing but you may have to PROVE it in court, and it may not be as easy or straight forward as you think. The decision could go either way on the day.
I have won four-out-of-four but I didn't enjoy any of it. Courts are not nice places to be!

Hooters Top Tips:-

Take photos, lots of photos. (I once won a case ONLY because I was able to produce convincing photos and stick them in front of Judges nose. The other bloke and his solicitor were tearing me into peices, it was awfull)

Be well prepared, copies for everyone, openess.

If you can give way on some small point do-so but be very careful.

It may help if you are proffesionaly qualified, but I don't think it's essential (in this case)

Try and keep stuff in the 'Small Claims' league if it is within your power

Better still, mediation may be a better option.

Assume nothing

Has the vehicle owner contributed in some way to the failure e.g. can he prove timely and correct service history, has he ignored previous relevant advisories, have YOU followed procedure.

Etc. Etc.