LONDON - The London Underground, the world’s oldest metro system, celebrates its 150th anniversary this week, still rumbling along and carrying four million passengers a day across the British capital. On January 10, 1863, after three years of privately-funded construction work, London’s first underground railway line opened to the public. Long queues formed at each of the seven stations for the chance to ride the line, in carriages lit by gas lamps and pulled by a steam locomotive. Passengers could travel in first, second or third class, and from 1874 onwards, in smoking or non-smoking carriages. The Metropolitan Railway ran for three miles (five kilometres) and had seven stops.