(click for full size image)
This isn't based on any detailed feasibility study. It's the result of a bit of Saturday afternoon planner's megalomania - a loose collection of existing strategies and schemes, with a few changes. Most underground lines are left out for clarity.
London has lacked high frequency commuter lines which go deep into the city centre, like the Berlin S-Bahn and Paris RER.
The Crossrail lines will help remedy this, and make it easier to commute from a long distance directly to the centre without having to change at a main line station on to a congested tube.
There's also an opportunity to create an Outer Circle Line - following the route of the London Overground network - to relieve pressure on the centre, make it much easier to travel between the north and south suburbs and improve connections with the airports. This would be a similar scale to the JR Yamanote Line in Tokyo.
For an outer circle line to work, it needs good connections with the radial routes heading in to London.
There will be interchanges at Clapham Junction, West Hampstead, Dalston Junction, Whitechapel and Shadwell, but there could also be valuable interchanges at Willesden Junction with Crossrail and the main line, and at Surrey Canal Road with the Thameslink line.
A link at Willesden Junction could also allow high speed trains to run directly from Heathrow to either Europe or the Midlands and Scotland.
There is a proposal to build a new link between Staines and Heathrow Terminal 5, which could potentially be linked to Crossrail Line 2.
In the North East, there could potentially be a new interchange at Hackney or the lines could merge at another location, providing a direct rail link between Heathrow and Stansted Airports in under 2 hours.
A New Thames Gateway Airport
London is looking at the feasibility of building a new long-haul hub airport outside London, probably on an artificial island in the Thames Gateway.
I don't have enough information to know if it's the right idea or not.
It would improve the quality of life for hundreds of thousands of people in West London, it would allow a state-of-the-art airport with fewer delays and plenty of expansion room. It would also release a large well-connected site in West London for thousands of new houses (despite the current recession, new houses will still be needed in London).
On the other hand, it would mean tens of thousands of people who work at Heathrow would need to find new work or commute a long way to the new airport.
(When the main airport was replaced in other cities eg. Paris Orly to Charles de Gaulle, or New York La Guardia to JFK, the number of people affected was much lower, and Heathrow would represent a totally different scale of upheaval.)
There is also a huge cluster of services, hotels, logistics, car parks and other businesses in the area around Heathrow, which would also need to move. Lastly, the airport would be in a very inconvenient location. There might be a decent train service to London St Pancras, but getting there from the rest of the country would be difficult.
It would be expensive (My best guess is £25-30bn by the time it was finished), but in the long-term this could possibly be paid for by redevelopment of the existing Heathrow site and savings from fewer delays etc.
What do you think?