Construction of the Metropolitan District Railway, London, c 1869.

UNITED KINGDOM - SEPTEMBER 30: One of a series of photographs by Henry Flather showing the construction, undertaken between 1866 and 1870, of the Metropolitan District Railway's (MDR) underground lines between Paddington and Blackfriars via Kensington. The line laid by the MDR from the 1860s onwards was designed to provide a rail connection for travellers between London�s mainline railway terminals, situated in a ring around the city centre. It now forms part of the existing District and Circle Lines on the London Underground. The construction work, utilising the 'cut and cover' technique, caused much disruption to London neighbourhoods. In this view, spoil is being removed from the excavations using windlasses and buckets. (Photo by SSPL/Getty Images)