Which Hanoverian king was mentally unfit to rule in the last decade of his reign?

Player #30201398, Not likely. His monogamy was a source of derision amongst the aristocracy in an age when it was expected that the monach have affairs or mistresses as a sign of his potency and royal doctors were extremely adept at recognising and treating sexual diseases especially syphilis so it would have appeared in his surgeon's notes. Porphyria has been suggested because of the colour of his urine but most researchers lean towards bipolar exacerbated by the medications he was being given.

I enjoyed the film "The Madness of King George". 1994 or 1995 I think, with Nigel Hawthorne as the king.