The Moscow route has long been BA's most premium passenger-heavy short haul route. There are a significant number of major corporates (finance, oil, etc) who fill the front cabins of the 767s currently used on what is without a doubt the highest-yielding European route for BA. However the standard of the 767 short-haul premium seats is poor, as has been the cabin service, in comparison to what obtains on Aeroflot nowadays, which has been the cause of much adverse criticism over recent years (there's a long-running thread by regulars on this specific route over on FlyerTalk about this), and BA have been in serious risk of losing their market.
It is surprising that BA went for a 747 rather than a 777, but presumably that's what they had available.
Presumably the cabbage pies in the Domodedovo lounge for these premium pax will be staying, though.
