It's naughty to do that. Late at night it is sometimes left open at both ends to assist the cleaners. Normally both ends are shut off, with the glass doors closed, but because it's an emergency exit it can't be locked. And because there are legitimate users I guess they don't want alarm bells going off all the time in CCR/FLounge and no-one knowing how to switch them off. If the gate is open during the morning - perhaps having been left open since the night before - I think you would be within your rights to close it.

However with that alarming first post (haha) we welcome KerryMLC to Flyertalk and the British Airways forum. Thanks for that first post and thread, may there be many more - hopefully less upsetting! Welcome on board.