Let's start by looking at the importance of boundaries. This is where I was born:
The little arrow marks 174 and 176 Beckenham Road, Beckenham, Kent. This address is located in the London Borough of Bromley. The Bromley Adult Education Centre used to be Cater Park School (alumni including Rachel Reeves, MP for Leeds West and my mum - although back in mum's time it was Beckenham Grammar School for Girls). The school is in London SE20 not Beckenham, Kent with the boundary between Kent and the London post code following the line of Royston Road and Kent House Road.
Back in 1961 all of this was in the County of Kent meaning that I was born a Kentish Man rather than a Londoner. The London Government Act of 1963 changed all this by creating the 32 London boroughs including the incorporation of Beckenham and Penge Urban Districts into the new borough of Bromley. By the stroke of a pen, my birthplace had shifted from Kent to London (although by the borough's creation we'd moved to Shirley, Surrey another bit of the new London).
All this came to mind from a little video posted on the Londonist website that showed the different boundaries of London - political, transport and postal geography are not, as the saying goes, co-terminous. The idea of London is pretty fuzzy - the futher you get from the original London (the Square Mile of the City itself) the more other place associations become important to people. Not just the distinction of North or South of the river or whether you're on the tube but identity with old towns or villages as well as the old county geography of Middlesex, Surrey, Essex and Kent.
So where I was born is variously in London, Kent, Beckenham, Bromley and, at a pinch since it's the nearest town, Penge (we lived later at 186 Beckenham Road where we knew we were in Beckenham because there was a sign outside the house saying so). Any or all of these answers would be correct for a particular question but equally that answer would be open to question. If I say "I'm from Kent" someone might retort with; "nonsense, you're from South London". And the same goes for all the answers - I'm pretty clear about my identity (it's all of these things) but defining it to someone who doesn't fully understand the relevent history and geography can get a little long-winded and confusing.
And I can hear you muttering "oh, shut up Simon, it doesn't matter". Except it does - Heathrow Airport tells us it does. Or rather the decision about airport capacity "for London" tells us why this argument about places, boundaries and history is important. Here's the current Mayor of London:
Mr Khan said the government's announcement was "the wrong decision for London and the whole of Britain".
He said ministers were "running roughshod over Londoners' views", and that the new runway would be "devastating for air quality across London".
There's more but this is enough for my point. As is remembering that both of Khan's predecessors opposed expanding Heathrow as did the man he beat to become Mayor of London. Now there are many arguments for and against different options but these are not the things determining the position of the Mayor of London. It's the bit about Londoners' views - Sadiq Khan, like Boris Johnson before him, is elected by those Londoners and they want more airport capacity but not actually in London.
Khan's argument in support of expanding Gatwick is about politics. The people affected by its expansion don't live in London so don't enter into the Mayor's calculations - there are a lot of votes to lose in supporting Heathrow but few, if any, votes lost by backing Gatwick. Yet had past spatial decisions beeen different - say a London limited to the old London County Council area or a different location (Croydon, maybe) for the airport - the Mayor might has been gung ho for supporting the third runway at Heathrow (or Croydon).
It seems that the bitterly contested (there were huge petitions from Bromley and Croydon opposing the changes) London Government Act of 1963 is largely responsible for the problem with deciding about an airport for London. That Act created the current boundaries making the new authority (as fans of Horace Cutler and Ken Livingstone can explain) politically marginal - those votes in West and South-West London really matter - and it placed Heathrow Airport within the boundary. So long as the outcome of London's mayoral election was contested, making a decision in support of Heathrow was fudged. The same thing that made me unsure about whether I'm a Londoner or a Kentish Man has also meant three decades of dither over the development of airport capacity that's right for the World's greatest city.