Let me chime in here. First here's the independent coverage:
http://www.independent.co.uk/travel/news-and-advice/british-airways-staff-forcibly-restrain-cancer-passenger-kwame-bantu-diabetes-london-jamaica-flight-a7705711.html
We are all just guessing here and from my albeit limited experience in detours and emergency landings the captain no matter what it was that happened wouldn't have made that decision lightly and most likely got approval from powers above. The costs involved in this are huge not to mention the PR nightmare.
I would like to ask a question though, with so many smartphones and cameras available why has nobody (crew) included documented and released the footage of the incident in J? I would think that a serious incident in J would spark at least a video out there... after all their are photos of crotches making it to TV!