Wingnut, perhaps it was me who you were referncing as "one FTer who went out through security and persuaded the guard to let him back in!" I can assure you that there was very little persuading or cajoling on my part.

All I did was walk up, say, "Good morning! I want to take a shower at the Red Carpet Club and they said I had to go through here and get my boarding pass stamped and re-enter through security. Would you stamp it for me?" With all the indifference he could possibly muster, the man took my boarding pass, slapped a security stamp on there, and waved me through.

It should be noted too that, for some strange reason (discussed at length in other threads) probably having to do with strong tea and overboiled food , LHR actually has a security gate that serves this precise purpose: to screen passengers who want to get back to where they were in the first place. It's literally a circle hallway that goes from T3 back to T3 with a security screening in the middle of it... I guess it's just if you feel like being wanded... or you want to get your boarding pass stamped so you can take a shower.

Pardon my air of cynicism.