BA's base is Greater London within the M25, not those outside the M25, The 58m matter a lot less (to BA, that is) than those who either have London as their origin (O) or their destination (D).

In 2023, London airports saw 168 million passengers. Among those, a mere 23 million were connecting. This makes London a unique market. And this is one reason why I discounted posts suggesting AFKL's Flying Blue and LHG's M&M will see a huge influx of members. This change is bound to have consequences, but don't expect folks from the city to start flying a bunch of AFKL or LHG. Probably, those in the FT bubble will adapt more than others. But most likely, they will change considerably less than they have been suggested during the last 24 hours.