This brings anti-competition issue.

oneworld currently dominates LHR-HKG - BA CX QF operates over 80% of the capacity but individually so they are still competeting (to a less degree tho).

British authorities wouldn't be able to justify such approval - it will damage customer's interests.

When CA CX KA codeshared all PEK-HKG routes, economy fare went rocket high and never came down.