If the car was currently defected, then I'm pretty sure the insurance company will deem it unroadworthy and you will have no insurance anyway.
Also, I'm pretty sure it's only legal to drive home from the defect, then to and from places of repair while defected.
I'd say he's unlikely to be charged with failing to give way to a car that he could not reasonably assume would be travelling at double the limit.
Sorry dude, but if you were doing double the limit in a defected car, then I'd say you're screwed.