Let me see if I understand.
The individual concerned has a medical degree from a top university. And he wants to join the Army, presumably not as a doctor.
Two things spring to mind:
1. What a waste of a medical degree.
2. Maybe it is his sanity that is in question, not his education.
Oh, I sense this wasn't the place to get helpful advice/ insight.
FYI Lots of people don't do careers based on their degrees. A four year medical degree does not leave you qualified as a doctor, or even paramedic, but this is going off on a tangent..BACK TO MY POINT - surely an indication of some level of academic ability.
Andy I hate to say it but even if the degree trumps A-levels he got a 3rd. When you take into account the poor preformance at A-level for whatever reason the accademic ability is obviously lacking. If he had done badly at A-level and excelled in his degree then that would show academic ability. No A levels and a low pass on a degree does not.
Good luck whatever he decides to do