I am a former getter-away-of-it. Was allowed through Fast Lane at LHR T3 as an A3*G. It was a bit embarrassing though, and I only suspect he let me in because there was a queue forming behind me.

I checked with A3 and I was completely not entitled to use the Fast Track - the payment they have arranged only covers elites travelling on A3 metal (and C class of course). In my defence, I thought the website reads like an A3*G could use the Fast track no matter what the airline you are flying (the M&B website is a little vague on most things really). Apparently, *G other than A3 are also covered when travelling on A3 - I think someone said they get an invitation on check-in, which is very nice of them.

Now I know the rules - I won't be trying this again. It gives very little advantage in this case (other than avoiding a longer walk through the LHR T3 shopping mall departures lounge.

Incidentally, I also used the fast track in LHR T1 when flying C on Asiana. Was waved through without a problem, though Asiana don't even pay for access for their premium pax (found this out later - just assumed they did) - so it seems I am a serial pushy rule breaker . It also appear then that the pass checkers don't really care if you are entitled or not and I'm sure anyone could push through if they really wanted to.