'The Tube' was initially a 3.5 miles line between Paddington and Farringdon, opened in 1863 in order to help transport a population which had grown to 2.5m.
A contemporary reports said some 40,000 people travelled the line on day one, very many of them curiosity passengers.
The trains were steam-powered, and the journeys were fairly sooty and noxious despite serious efforts to improve ventilation. Electric trains were introduced in 1905, which solved the problem.
