When I read stories like this it makes me sigh. It's not particular to BA, most airlines are doing similar things and really they've bought it on themselves.
They start by charging for checked-in bags.
Many passengers start bring their bags into the cabin, with far too many bringing the proverbial kitchen sink with them.
The airlines are surprised when there's suddenly insufficient room in the cabin for everyone to stow their bags.
Planes leave late because of all the faffing around dealing with all these bags (including the kitchen sinks).
Dragons are sent out into the crowds at the boarding gates to pressgang people to give up their bags.
Wasn't all this so predictable?