In this case, all the bolds are unreliable.
On their own maybe, otherwise given the nature of the evidence, and taken as a whole, it is likely to be coherent, and compelling.
Left the phone at home that day, anyone could have been using it.
That would unlikely be a robust defense, given that the phone company would likely be able to give a location for the phone at the time of the call.
Consider if there was CCTV evidence with a time stamp, there is likely to be metadata attached to the image corroborating the time, his phone records would then confirm if a call was made (or received) at this time, as well as his location of course, it's entirely possible that the person he was allegedly talking with would be called as a witness for the prosecution (because lets face it, they wouldn't be a witness for the defence would they

) now given all the potential evidence above, would this person really run the risk of committing perjury to save Clarksons arse?
Of course, he could also be prosecuted for driving without due care and attention, which itself would carry a reasonable fine and 3-9 points.
Humour aside of course, if he is guilty I hope he is made an example of.
Seriously.