I think, as has been mentioned elsewhere, it should be remembered that BA contracted to deliver this passenger from A to B safely and without incident.
Clearly this didn't happen.
As such, he's within his rights to demand compensation, and to enforce that demand through the courts. This seems quite fair and reasonable to me, provided that the compensation he receives is proportionate to any physical / mental trauma suffered, whether such injury is permanent, whether it has a short or long term impact on this gentlemans quality of life, and whether there are any mitigating circumstances (like the pilots saving his life).
So I would suggest......£250?? Out of which he'd be obliged to pay his legal costs of course
