The 911 piece was not a Top Gear video.

An MOT is only valid on the day of the test. Rusting wheelarches, dented bodywork, failed electrical systems - none of these are required for a vehicle to pass. It just has to demonstrate adequate roadworthiness. Even the ABS system or airbags aren't required. It may have been in an accident and suffered significant damage - but still hold a valid MOT.

At the end of the day, if it was £700 there was a good reason for it.

A tax disc has nothing whatsoever to do with the condition of the vehicle.