Originally Posted by number_6
Irrelevant to your problem, as you were not a J passenger at LHR. Downgrades suck, but you lose any residual rights when you take them. If you don't like this system, fly enough to earn FF status and get lounge access based on that (which is much easier and more predictable). It's rather trivial to earn J lounge access by becoming OW Sapphire.
The EI lounge attendant at LHR disagreed with you. He conceded that I was on a J itinerary, but said that
that was irrelevant, as no business class passengers were admitted based solely on ticket.
The EI website says the exact opposite, that business class passengers
are admitted to all lounges.
Seems like one or the other can't be correct.