It's public Transport, it's in London, slow is a foregone conclusion

The problem with our rail system is that it spent about 5 years doing absolutely NOTHING except make money after it was privatised, it forced retirement on it's oldest (and most experienced) Engineers to save money, they dropped the contract with a track manufacturing company who's rails had never broken though weathering, to one who's rails suffer terribly from cold-stress, etc...
The only way to fix it is to give every Rail Commuter a week off work, employ thousands of Engineers/Labourers and stop British Rail for one week while they replace a large percent of the inner city Networks. This is about as likely as British Rail running MagLevs.