Not a BA lounge, but I got very merry in the tiny Highland Lounge at Inverness Airport.
I created my signature drink; a T&G* and had five triples. Then I ordered one on the 'plane and had to grab the sickbag. That was the first time I realised I had actually drunk too much, and it was inadvertent. Thankfully, I fell asleep and when I woke up near Luton felt much better.
* A T&G is a dash of tonic, topped up with gin. The triples I had all contained one little dash of tonic.