Long Distance Haul

Can someone tell me where London ends? Because it seems to be stretching further every day. Yet another airport is now billing itself as "London", this time it is London Oxford. Anyone who has been to either London Luton or London Stansted already knows that these are a signficant distance from the city itself. No commuter in their right mind would pick either of these if they wanted London for the day. And using either of these two I have previously wondered how they get away with the "London" tag. But Oxford, a beautiful city with great history and heritage, why would that even want the tag of "London". It doesn't make much sense.