Why did the underground railway soon become a necessity in London?

Why did the underground railway soon become a necessity in London? Mention any three disadvantages of this system.

AFTER the industrial revolution like other cities, London became very crowded when people began pouring in. The major problem which cropped up was of housing. Factory and workshop owners did not house the migrants. Instead individual land owners put up cheap tenements for the working class which were neither safe nor properly ventilated. Attempts were made to decongest the city of London and solve the housing crisis. Meanwhile the city had expanded beyond the range where people could walk to work. Thus, the developments of suburb made new forms of mass transport absolutely necessary. The London underground railway (set up in 1863) solved the housing crisis by carrying large masses of people to and from the city.
The disadvantages of underground railway:

  1. The underground railway added to the mess and unhealthiness of the city.
  2. To make approximately two miles of railway 900 houses had to be displaced/destroyed. Thus, London tube rail led to massive displacement of London poor.
  3. The underground railway was considered a menace to the health due to the lack of oxygen created in the compartment by smoking pipes, fumes of gas lamps and coal dust.