I dont think the car is even physically able to go that fast just for the fact that you dont have enough RPM in 6th gear to even get that fast. Not to mention that with the amount of power these cars have (considering its an older one if it was sold for £9,000 ), it would take FOREVER to get to those speeds.
Now heres something more interesting. The police claimed he was going 175MPH. The court then settled that he was going 105 MPH. 105 MPH = 168 KPH....maybe the explanantion was operator error.