I think there is still one big flaw in your argument, he STILL HAD 3 ILLEGAL TYRES, which ment he SHOULDNT have been on the road, the car was unroadworthy and should NEVER have been on the road in the first place!!!!!!!!!!
It should be the same as if he never had any insurance, he shouldnt have been on the road, therefor the accident should have been his fault!!!!
Its not that hard to dip the oil and do the relevant safety checks to your vehicle once a week!!!!
Graeme