I'll soon be travelling in Economy from/to OSL to/from HKG with BA (OSL-LHR) and CX (LHR-HKG) - everything on one PNR.

What is the checked baggage allowance for a BA Silver member (OW Sapphire) when connecting between these two OW-partners?

I'll be travelling in Y both ways. I know BA have special allowances on checked baggage for BA Silver members, but what is the rules when part of the trip is with Cathay Pacific?