I can't be the first person wanting this but I can't find the answer on forums.. can I redeem say LHR-SEA on BA metal following by SEA-ANC on AS using avios in one booking? I know it must be done by phone but is there any issue with redeeming a mix of BA and non-OW partner under one booking? I think OW partner (e.g. AA) mixed with AS is a can of worms I don't want to touch!