Originally Posted by
GCab
OK so fallen at first hurdle - what have I done wrong here?
An itinerary using BA between LHR and HKG requires a BA fare.
An itinerary using CX between LHR and HKG requires a CX fare.
A BA fare outbound cannot be combined with a CX fare inbound. Or, at least, that is my strong suspicion as the reason for what you have found (or, rather, failed to find).
That's why you must have a BA flight from HKG to LHR inbound to stay at this fare level. But that may then make your desired CX unavailable to you.
And that is the magic (for airlines) of playing married sector games.