I don't fully understand this... did you present an onward AC BP or just your arriving AI BP? Is the LHR arrivals facility open to all LHR-terminating SE's arriving on any airline at T3?

The reason I ask is that when I fly revenue J (D-class) and enter the MLLs the agent automatically and immediately looks at the lower right-hand corner of my boarding pass looking for the "C2/Y10" entry designating me as a non-rev. I've always wondered if they did this because I am a young guy or if they do it to everyone.

Anyway, I can't believe the LHR folks would let someone flying on an (I assume) C6 BP slip into the lounge, whether it was accompanied by a SE card, or Robert Milton's driver's licence for that matter. If you have had good luck in masking your true status, more power to you, but as Gazou2002 said, please tread lightly. AC regards non-revs who try to procure premium services on the sly with the type of loathing usually reserved for child kidnappers.