[Enchante]

that can’t possibly be all of London, there are around 2 million voters in London (last Mayoral election).... it’s not all “out of the way” by a long shot

[bunster]

ITV said it was just the City of London - very low population

[naturalman1975]

That can’t possibly be all of London,

You're right - it's not. The City of London is the area that was once surrounded by a wall in the Middle Ages and which today is considered the financial centre of the UK (and still sometimes gets described as the financial capital of the world). It's only one square mile in size and is full of office buildings - hardly anybody actually lives there.

Greater London surrounds it.