Diana was very innocent when she married Charles. By the way.

But: I think that Fiat Uno driver wasnt in tunnel for doing anything but just accidentally. He was maybe a farmer with big dog. But he saw what happened between a motorbike and mercedes and how did those men behave there. Fiat Uno driver was an innocent outsider which decided escape rapidly after all that.

But I am sure he just want to tell something sometimes ( if he was not eliminated afterwards).

Farmers have big dogs...