Check an address and interview anyone resident there in a way that gets useful answers to the questions at hand.

In this instance it was a bust because no one useful was there. But if the mastermind behind the whole operation was there you’d want a professional to ask them questions. Because once they know they’ve been rumbled they’re probably going to disappear.

I am pretty sure the BBC, like most bug enough news outlets, has antennas all over the world.