Sorry, what? Are you honestly that stupid? God probably does know how many other airlines fly 'our' route. So do many others.
BA - 2 x Daily
VS - 1 x Daily
CX - 5 x Daily
Let's have a look. Let's even pretend that all the aircraft used are the same, because it seems simplification is a trait which you'll value.
Twenty years ago, BA operated two flights a day. CX operated one. During this era, BA had a 66.6% market share. CX had a 33.3% market share.
Now, BA have a 25% market share. VS have a 12.5% market share. That's (25+12.5) 37.5% of the market which CX don't have. 100-37.5=62.5
Using such simplification, CX have a 62.5% share of the market. By my maths, I would suggest that 62.5 is a bigger number than 33.3, therefore I would make the assumption that CX market share on the HKG-LHR city pair has INCREASED. In fact, it's nearly doubled. Do I think thats good? I do. Now, factor in aircraft size, and we'll learn that BA have a larger market share than 25%, and CX less than 62.5%.
Now, I know you're an all-important pilot and everything, but for a moment, consider how stupid one question can make you sound. Folks far above your pay grade, at a very high commercial and political level negotiate for the rights to operate international flights. Such permissions come with value-reciprocity between the two nations.
If you think that CX could have kept on growing HKG-LHR city pairs without IATA and government bodies allowing other relevant airlines a fair crack at it, you're extremely ignorant of the process involved. Let's face it, BA are the only real competition on the route. CX are not going to be given carte-blanche to launch more and more flights on the route without BA being given reciprocal rights.
In a slot-limited destination such as LHR, as other airlines fail to operate the route profitably, CX or anyone else have the opportunity to try to snag it. For example, 237/239 which was ANZs loss.
Having watched airlines come and go on the route, I'd say CX is reasonably dominant of the market.