Well if we stick to the letter of the rules in theory there is only an obligation to the Gold card holder (who is over 18) travelling on BA to let them into the lounge; as the 1 guest is '*Subject to capacity' and so if the lounge is full then really they only need to let the cardholder in. However in practice there is a lot more flexability and I think that is how it should be. If the lounge is empty and the Gold Card holder has a couple of guests and they all look respectable and if children then they should seem well behaved then I think they should be let in - as long as it is made clear that this is a one off and is not the norm.

What is interesting is when travelling in First even a blue can invite a guest into the Concorde room.

Also when using Gold Access Anytime they cannot invite any guests (when not oneworld) and can only use the terraces.

I wonder if they in practice are more or less generous to Oneworld Emerald than BA Gold?