BOAC
Thanks
If I were an FO and convinced that the commander was not in a fit state to command, he/she would not accede and that not acting would likely result in loss of control , I would take command and if challenged subsequently in law, invoke common law defence of necessity and public interest.
Above Captain NF intimated that he was confident that such scenarios would always be resolved amicably. I once read a story about two ( Turkish ?) pilots fighting in the cockpit and spillig out into the cabin- is that one for the 'apochryphal ' file?
Anyway grateful as ever to you ( and Cpt. NF) for taking the time to raply.