THE world?s first underground train, on the world?s first metro system, travelled the three-and-a-half miles from Paddington to Farringdon on January 9th 1863. Then, as now, Londoners queued to get aboard the packed carriages. In October that year The Economist ran an editorial arguing that more such lines under the capital were needed to relieve its congested streets. It concluded that such a network, if well run, would surely be profitable.We were right on the first point: London would have ground to a halt long ago without its ?Tube?. But we were too optimistic on the second. Although fares on the Underground are now among the most expensive of any metro system worldwide?a one-stop ride costs up to £4.50, or $7.34?the system is no money-spinner. Last year, the £2 billion of fares revenue, added to the smaller amounts from selling advertising space and suchlike, only just covered running costs, at £2.2 billion.