There are two different ways of measuring distance. (Actually, there are more, perhaps infinitely more, but for the purposes of this story we shall go with two.)
You can do it as-the-crow-flies, drawing a straight line to find the shortest distance between two points; or you can consider how long it would actually take you to get from point A to point B. Of these two methods, the former has the advantage of being objective, scientific and accurate; but it's the latter that actually chimes with human experience of the world.
Which brings us to this rather clever map we found on the website of entrepreneur, occasional CityMetric contributor and professional Yorkshireman Tom Forth.
The map shows how well connected 22 British cities are by rail. Click on any one of them, and you can toggle between one map showing physical distance, and another showing how long it’ll actually take you to travel to other cities by train. (This is something called an “isochrones” map.)
To make things even cooler, the travel time map overlays a warped, pink version of the British isles. By comparing it to the geographically accurate white one beneath it, you can get a very rough idea of which bits of the country take longer to get to than you'd expect them to.
All that's probably a bit difficult to visualise, though, so let's actually try it out.
Let's start with London. Despite being tucked away in one corner of the British isles, the capital is the centre of Britain's rail network, with direct trains to basically everywhere. Consequently, it doesn't warp the map too much:
How far from London is the rest of the UK? On the left is physical distance, on the right is travel time by train.
A few places in the flung corners of the British isles – Plymouh, Norwich, Inverness – are slightly further from that capital than one might expect. A few areas (lowland Scotland, Devon) take a surprisingly long while to traverse by train.
But other cities – Manchester, Liverpool, Edinburgh, Glasgow – are pulled slightly closer on the isochronal map. That's a measure of the fact that both the East Coast Main Line into King's Cross, and the West Coast version into Euston, are actually pretty nippy.
Generally speaking, though, the travel time map is a pretty similar shape to the geographical one. This isn't going to last, so enjoy it while you can.
Now let's look at what happens when we click on Birmingham. It may not be at the centre of Britain's rail network, but it is in the middle of the country, so you'd expect the map to look pretty accurate, right?
Distances from Birmingham. On the left is physical distance, on the right is travel time by train.
You can instantly see that it takes longer to get to almost anywhere if you're starting from Brum than it does if you're starting from London. The pink overlay is waaaaaay bigger than the map underneath.
For a good example, look at Norwich: only 150 miles from Birmingham, but a good four hours away by train. That's an average speed of less than 40mph.
We can keep playing this game for hours. Plymouth is so far west that it takes two hours just to get to Bristol; on the isochronal map, Norwich is practically on Dogger Bank, and, as for Scotland, forget it.
Distances from Plymouth. On the left is physical distance, on the right is travel time by train.
From Norwich it takes at least three hours to get basically anywhere:
Distances from Norwich. On the left is physical distance, on the right is travel time by train.
Distances from Inv- oh, you know the drill by now.
And don't even get me started on Hull.
It's probably risky to draw too many conclusions from all this: we're only looking at one form of transport, so it’s a bit premature to argue that Norwich, say, is isolated from other cities.
But we can say a few things. It seems pretty clear that the cities best connected to Britain’s railway network are those that are on a few major arteries (most important, the East and West coast main lines). Hull's relative isolation stems from the fact that it's on what is in effect a branch line.
It also helps to have fast trains in more than one direction. It doesn't take that long to get from Norwich to London, but that's not that helpful when most of Britain's cities are in the other direction – and trains out of Norwich to the west are distinctly plodding.
Anyway. If you're the sort of person who likes playing with these things, and why wouldn't you be, then you can do so on Tom's website here. You should also, since he’s been kind enough to let us nick his maps, follow him on Twitter.