How to design a city?

You address a very important point. However, if we stay on the subject of transport planning for a moment, when you say that London hasn't been designed, this is only true in the sense that until the 20th century there weren't big masterplans trying to encompass everything. But what was already there before were powerful interests that strongly determined what was done.

Take the root causes of why London is such an over-dominant megacentre that sucks the lifeblood out of large swathes of the rest of the country. London's patterns of suburban railway development are overly radial, which causes crippling over-centralisation, as powerful interests dictated the over-development of the centre.

In theory, London is one city the size of Berlin and about four cities the size of Munich (say, one centred at each of the cardinal points of the compass). But because its transport patterns effectively prevent the cohesion of the outer parts, it is more like a city the size of Berlin and hundreds of villages. This draws disproportionately many people into its over-congested centre.

I really wish that London had been shaped 'by its people' but the reality is that it has largely been shaped by business interests. Planning law is heavily skewed in favour of developers, or take Crossrail now--another railway line smack bang through the centre of London, which will cause further over-centralisation. Business considers this line so important that it is even willing to contribute to its costs (a little).

You're absolutely right that the kind of blank slate planning that has produced Milton Keynes isn't an ideal way, either, but London is just too extreme in almost every way to serve as a template for desirable city development, and certainly don't agree that it has grown up to suit the needs of Londoners (and I do take your point that we can't have it all to suit us ideally). There are places that I for one really like in London, and I'm sure everybody has those places, but I can very rarely feel much of a sense of ownership of these places. London is something that fills me more with a sense of awe than with love.

It's a difficult balance to achieve between over- and under-determining things, and perhaps putting in place a basic template on which people can subsequently exert their own creativity in a sustainable way is impossible. In the meantime, we have to make do with what we've got and do exactly what you say: change London to make it suit the needs of Londoners:

http://www.transitiontowns.org/

http://www.localworks.org/

And, of course, London needs more walking and cycling, to knit those local places together with a proper social network and enable more sustainable living.

The reason London is centralized is because up until only comparatively recently the cost of distribution of goods and services was so high that commerce required a high density of population to make it profitable and worthwhile. Now-a-days you can buy near enough everything on-line but when I was a boy if you wanted something unusual or outside the mainstream that meant a trip to London. Commerce is whats makes London tick and the railways were built by entrepreneurs catering to a demand from people who wanted access to the goods and services that only London could offer. Far from London sucking 'the lifeblood out of large swathes of the rest of the country' I'll think that you will find that London's commerce bank rolls much of the rest of the UK generating as much as 30% of UK's GDP. This is not to mean that decentralization is not the way forward in the age of the Internet but it is worth remembering that decentralization is a modern luxury not afforded by our heritage cities.