Should be pretty straight forward to deal with. A GP should be able to provide whatever info is required. If theres a ‘notfifiable condition’ ( you’ll find a list of them here) (or vouch that there isn’t a notifiable condition) also a GP can still vouch as to whether that condition impacts on driving.
If they can’t then you’d need to do an NHS driving assessment – which I’ve done and its really interesting. The tests you need to do to keep your license are far more interesting and involving than the test you pass to get it in the first place! However – the waiting list of assessments can be pretty long. In my case they seemed to have one assessor covering the whole of scotland (in a mobile testing facility sitting on flat tyres in a hospital carpark somewhere in the outskirts of Paisley).
If its an act of random vengefulness then fair enough. However if theres a condition thats being kept under wraps and the whistle has been blown, even out of spite, then its worth taking seriously even if its a bitter pill to swallow.
People never doubt their own fitness to drive, and if something does go wrong down the line knowing about but not declaring impairments can blow up in your face pretty spectalarly.