London's sewage network is experiencing a major upgrade, with the Thames Tideway Tunnel super-sewer starting construction in 2017. It will span from Acton in west London to Abbey Mills in the east, travelling under much of central London as it goes.
However, ahead of the Tideway tunnel's completion, here are six things we learned by going down an actual, in-use Victorian sewer.
1. The sewers actually don't smell of what you think they do
They really don't. Instead, they smell "earthy", "musky" and "like compost", among other adjectives.
This is because around 98 per cent of what flows through the sewers is liquid rather than solid, and includes run-off rainwater and all the water we use from dishwashers, washing machines, showers and taps, instead of just toilets.
2. Your fibreoptic cables have probably been laid in the sewers
To avoid digging up most of London to lay fibreoptic cables, broadband and telecoms providers have conveniently piggy-backed on the walls of London's sewers, criss-crossing the capital so everybody can watch Netflix.
The cables have been especially designed to be larger than the mouths of common European rats, to avoid them being chewed through.
In the below picture, you can see yellow-spotted fibreoptic cables snaking along the roof of the sewer.
3. The sewers contain intricate brickwork and impressive architecture
The hand-laid brickwork in the sewers is an impressive feat of erosion-defying engineering. Above the ground, the Abbey Mills pumping facility's main building is an impressive Byzantine and gothic-inspired venue. It was the only part of the original intercepting Victorian sewers constructed between 1859 and 1865 that was above ground.
Colloquially, the Abbey Mills pumping station is also known as the "Cathedral of Sewage".
4. Don't ever, ever flush wetwipes
This point is definitely not picture-friendly, but trust us: wet wipes do not disintegrate.
Instead, if you've heard of "fatbergs" (Google further at your own risk), which are essentially solid, congealed collections of fat that smell foul and clog up sewers, you can rest assured that wet wipes are a major culprit in their creation. Almost anything sticks to them, and it gets as foul as you can imagine.
5. The men who maintain London's three sewer depots are called "flushers"
Well, technically their job title is "Sewer Technician", but the Victorian name "flushers" has stuck around.
London's 60 or so flushers are based across the three main sewage depots in Hammersmith, Greenwich and Wick Lane, in east London.
6. It's a wonder that the sewers have lasted this long
The current sewage network in place was designed to be used by around four million people, but it supports double that amount now.
London's eight million-strong population is somehow surviving with Victorian infrastructure, although the plastic piping used now is still a world away from the old wooden piping that was originally used (below).
(Pictures included in text copyright of Greg Sigston/City A.M.)