I don't think in this case your comment eal401 is fair to the crew. The rules were clear. There is a process involved in removing a passenger which involves more than just the cabin crew. we don't know exactly how this passenger was treated and neither do you eal401, we just know he didn't have the paperwork required to travel on this flight and was offloaded. I think the big question should be why different airlines traveling in and out of the UK can come up with entirely different policies for the same thing.
Cathay now also provide a system where frequent travellers can register any medical conditions they may have this means they do not have to have clearance each time they travel. Maybe BA and other airlines could look into doing the same. It could be something which the airlines can include in their alliance programmes like they do with exec cards or even as part of that system. I wouldn't have thought it would require much effort.