As Chief Engineer on London’s Metropolitan Board of Works, Bazalgette was primarily responsible for the creation of the extensive network of sewers under the streets of central London. The new sewers made probably the single greatest contribution to improving the health of Victorian Londoners and the bulk of the system remains in use today. In addition, it physically changed the appearance of riverside London and the nature of the River Thames.

London’s rapid growth had not been accompanied by the infrastructure improvements needed to deal with the huge amount of sewage produced each day. Instead it was contributing to waves of cholera outbreaks and other public health crises. The River Thames had effectively become an open sewer and the Great Stink of 1858, when the stench from the Thames could no longer be ignored, was the final straw.

Bazalgette's engineered solution was a system that channelled the waste through miles of street sewers into a series of main intercepting sewers which slowly transported it far enough eastwards so that it could be pumped into the tidal Thames - from where it would be swept out to sea. The project was a massive undertaking. Fortunately for modern Londoners, Bazalgette insisted on constructing wide egg-shaped, brick-walled sewer tunnels rather than the narrow bore pipes previously favoured by Edwin Chadwick and others. This has allowed the system to cope with subsequent increases in volume.

Despite Bazalgette’s ingenuity, the system still dumped tons of raw sewage into the Thames - sometimes with unfortunate results. The death toll from the sinking of the pleasure boat Princess Alice in 1878 would certainly have been smaller if it had sunk elsewhere on the Thames. As it was, it went down close to one of the main sewage outfalls. Approximately 640 passengers died, many poisoned rather than drowned. Horror at the deaths was instrumental in the building of a series of riverside sewage treatment plants.