An explanation re the GPS track (thanks Tony!)
the website's gps tracker was linked up to software on Alastair's and Dan's phones. The exact phone in use was determined by battery, signal, who was awake, which vehicle was following etc. The tracking phones were always in different vehicles. My understanding of the speed confusion is that the 2 phones' locations were uploaded to the online tracker immediately after one another, with the vehicles being a few miles apart. As a result the gps location could potentially have "moved" a few miles over a couple of seconds therefore showing some crazy speeds! Hope that helps explain things a little!
So it wasn't Tom's driving after all 🙂