Flying Trains.

Southeast England, as I have mentioned previously (29th May 2006), is terribly short of housing. This is because Britain's economy is entirely dependent on London, while the other cities are reduced to the status of backwaters. As a consequence, everyone wants to work in London, and it follows that they want to live in the London commuter belt, which is basically, Southeast England. The problem can be partially aleviated by more high-rise buildings, but however well designed these may be, there remain practical limits on how many people can be crammed comfortably into a given area. Furthermore the increased concentration of people puts a tremendous strain on the transport infrastructure. By contrast the cities of the north maintain much lower land values, and suffer a comparative economic malaise.
In short, everyone wants to work in London, because that's where the business is, and everyone wants to do business in London, as that's where all the people are- a 'catch 22' situation.
The enviable French 'TGV' rail network, has achieved a world speed record for a (non-maglev) train of 320.3 mph ( http://en.wikipedia.org/wiki/TGV_world_speed_record ), but this was for a fairly conventionally designed train, and was attained way back in 1990. One would hope that British ingenuity could surpass this figure, to create a railway capable of averaging this speed. This is a matter of slightly increasing the top speed and maximising the acceleration that the train can accomplish. The introduction of 'broad gauge' would allow large wheels and thus reduce the wear they would otherwise suffer. A simple calculation shows that a dedicated track running in a straight line between London and Manchester, for example, could then be expected to be able to run a dedicated ferry service that could take a commuter from one city to the other in 35 minutes. Such an arrangement would place Manchester inside the London commuter belt. A similar service between London and Birmingham would be even quicker. Suddenly the pressure on housing in the south will decline, in competition with more widely available accommodation in the north. for the same reason the latter will come to enjoy the affluence currently monopolised by the Home Counties, business opportunities will expand correspondingly, and so will national prosperity- more than compensating HM Government for the subsidy that would inevitably be required to keep such a service running affordably.