insurance companies arent stupid. they will know that the middle aged man or woman isnt really the main driver of the cosworth but the young son who happens to be a named driver is and the premium will likely reflect this. how can it be proved in a crash situation anyway that it isnt co incidence that at the time of any crash just happened to be the first time the son had used the car?
basically he's 20 with no driving/insuring record of his own and no ncb because the bonus is his dads. he wont have a chance.