In the early years of the underground, in the 1860s, up to 60% of the track was actually above ground, and where it was below the surface, it was not deep and was constructed using a cut and cover system. However, there were major problems in dealing with existing facilities such as water supplies, drainage and sewers. This led to later underground systems being built deeper down so they could avoid pre-existing systems. However, they had to be dug by hand, and when they went under the Thames were at risk of flooding.
The advantage of the underground was that it could move vast numbers of people quickly and avoid traffic jams on the roads above where horse drawn vehicles still predominated. The first underground trains were driven by steam engines and this presented a number of problems on how to get rid of the smoke. Stations had to be built with open windows to let the smoke out, and because of the smoky atmosphere there was a promotional campaign to suggest smoke was good for asthma.
The first deep underground line ran from Stockwell to London Bridge, and because it was deep underground, the first coaches had no windows, but these were disliked as passengers could not see which station the train had arrived at, so windows were soon reinstated.
The longest escalator down to the platform was at the Angel. Lighting is an issue at underground platforms, and white tiles are widely used on the ceilings to reflect as much light as possible. The tile patterns on the walls were different at each station so passengers could recognise their destination when they reached it even if they could not see a sign (or if they could not read?)
A succession of architects are famous for having designed underground stations. There were some guiding principles that governed their design. The need for light meant that most had big windows, which let in as much light as possible during the day, and at night interior lighting shone out, advertising the presence of the station. Because land was scarce and expensive, they tended to have flat roofs so that multi-storey offices could be built over them. As the underground became deeper the stations went with it, so in many cases all there is above ground is a sign and steps leading down.
Where the underground extended out to more rural areas, stations were built to a design more in keeping with the area. They might be built to look more like a house in the country for instance.
Mark provided a great deal of information about the underground system which members with a rudimentary knowledge of London were easily able to relate to.