So one thing I can't help but wonder, is why they would choose to fly through Heathrow on the way to Rio, when there are any number of more convenient airports to fly through.

There's the obvious Lufthansa/Frankfurt connection he could have used, or the almost pleasant KLM/Schiphol route (which also seems the quickest from a cursory glance at hipmunk).

All of the other saturday/sunday flights that seem to pass through Heathrow to Rio are several hundred dollars more expensive and/or a five or six hour longer journey.

I suspect they were baiting the UK government, and were expecting this kind of retaliation. While it worked, it still feels kind of 'daily mail' of them.

Obviously it's circumstantial, and it could simply be that the Guardian had an existing account with BA or something as innocuous as that.

All I know is that you couldn't pay me enough to endure the horrors of Heathrow unless there was absolutely no other way to avoid it. And that's without the threat of the UK government possibly detaining me.