The door of the steel box lift clanks shut and a crane slowly lowers construction workers building London’s “super sewer” 40 metres to the bottom of an enormous vertical shaft.

Here, a world away from the city’s busy streets, thousands of engineers and construction staff have spent the past seven years creating the biggest-ever upgrade to the city’s 19th-century sewers.

London’s existing sewerage network dates back to the second half of the 1800s when it was designed by civil engineer Joseph Bazalgette in response to the infamous “Great Stink”.