Now for some comment.

First, it was pointed out to me that counting routes and airlines in units like this could result in unfairly over-stating the extent of the competition. For example, BA's competition to CPT is an airline at LGW, but that only operates seasonally and only about three times a week. It's a fair point, but that's a limitation of my methodology, which I set out in the post. However, this does not mean that the competitor does not represent real competition: in that specific example, I know of people who (like me) are travelling to a wedding near Cape Town and who were disappointed to find that this alternative was not operating at the relevant time of the year. So within the limitations of what I was doing, I think that a broad picture can be portrayed by this means even though there are specific instances where there's some fuzziness about a specific route.

Second, at first glance, this picture didn't seem to be obviously at odds with what one might expect at the major hubs of other comparable airlines, on whichever continent. For example, if one did the same exercise for ATL, CDG, DFW, DXB, FRA, HKG, SIN or SYD, it would not be a surprise to see the same sort of picture.

Third, and perhaps most important, it is clear that BA does have a dominant position at LHR. That is to be expected: it's BA's biggest base and arguably its only true hub. But it seems equally clear that BA does not have a monopoly at LHR. There are a few routes on which BA offers the only direct service from London, but it's a small percentage of the total number of LHR destinations. Most of the destinations to which the non-BA competition operates only from other London airports are served from LGW, which is a relatively straightforward inter-airport routing (required by quite a number of BA connections anyway). And even if your travel plans mean that you can only fly from LHR (perhaps you must connect without leaving the airport), then two-thirds of LHR destinations offer at least one other airline. And so, it seems to me, claims of a "BA monopoly" at LHR do overstate the true position.