If the government want to control drinking at airports, setting the minimum price of alcohol (by virtue of taxing them at 500% or something, haha), removing self-serve, and introduce fines for people serving alcohol to intoxicated customers* would be better than a ban.

*Possibly the 'responsible service of alcohol' style, similar to Australia where you have to complete a course and face a rather substantial fine if you disobey

Keep duty free at the normal price but make it an offence to open duty free alcohol at airports so that people won't be swilling it there. Perhaps 'delivery at gate' system like they have at SIN for flights to Australia etc.?

That way, people still have a choice - drinking just costs them a lot.
It won't face fierce objections from airport-based shops that might lose revenue through the morning alcohol ban, and airlines would happily charge for alcohol 'since they are required to' by the government. Then the government will be happy to collect exorbitant taxes on alcohol (which should then be allocated to the NHS since alcohol does cause extra NHS spending).

It might just encourage BA to offer a better range of non-alcoholic beverages in their lounges - or may be not, to encourage more spending on drinks