Nothing to struggle about really if forgetting for a moment the London-centric bias of this forum: it will be routinely a lot cheaper to buy ist-xxx in j via lhr on ba or ist-xxx via cdg on af than ist-xxx nonstop on tk so plenty of people do just that in the same way plenty of people on lhr-isr have r lhr-cdg are simply connecting elsewhere for much less than the cost of a nonstop on ba.