London’s new super sewer, the Thames Tideway Tunnel, has finally been completed after 10 years of works.

The sewer was first announced in 2012 as an addition to London’s ageing Victorian sewer network. While the original network was considered an engineering marvel at the time, London’s population exploded from around 7,000 people per sq km in the late 19th century to around 18,000 by the turn of the millennium. The older sewer also has to contend with increasing levels of extreme rainfall brought about by climate change.

With the original network not having the capacity to deal with these changes, excess sewage was being discharged straight into the Thames on an increasingly regular basis, breaching pollution guidelines.

The last of 21 connections to the original sewer has now been completed, allowing the entire system to be brought online for the first time. According to Tideway, the firm behind the project, the system should be able to prevent around 95% of sewage spills into the river...