Apparently there's been a change of policy now where the Concorde Bar at SIN is no longer accessible to pax not in F but have a CCR card.
See
https://www.oneworld.com/ffp/lounge-...eaccess/SIN/-1 vs
https://www.oneworld.com/ffp/lounge-...eaccess/LHR/-1
Can anyone else confirm whether this is supposed to be the case?