London is full of crap. So says anyone up North, and anyone who's been to Chiltern Firehouse. There is some undeniable truth in this though, in the most corporeal sense, since the sheer numbers in the capital means a lot of waste is produced.

Thankfully we have a sewage system in play that takes away all the filth from our homes, out of our streets, through huge pipes and out to sewage plants that treat, destroy and rid the city of all effluence -- so we can continue to live as if we are pure, clean, tasteful, elevated, shaved and manicured humans way above the animal world, and not the disgusting creatures that we are. Isn't it about time our sewage systems had a bit more respect for this service they give us?

One way of doing that is to visit the Crossness Pumping Station near Abbey Wood, which is a spectacular Grade I listed building that was called "The Cathedral on the Marshes".

While it is situated on one corner of the vast Crossness Sewage Treatment Works, and is the property of Thames Water, it is leased out to the Crossness Engines Trust, a charity which operates completely independently from Thames Water. Its volunteers have been working for more than 30 years to restore and preserve the building and its huge, unique engines.

Now, it's a bit of a pain to get to. Wise folk will get an Uber from Abbey Wood station to the plant or the old Routemaster that runs on open days. Idiots like me take the 30-minute walk. Once you arrive at the works though, there's a cute little train -- lovingly restored -- that takes you off down the side to the old pumping station itself, which is only open on certain days to the public, and must be pre-booked.

Demand is such that the charity is raising money chiefly to open on more days -- its Sunday steaming open days, when they get some engines going, are particular sell-outs. Mariam Ridley from the trust took me on a tour of the place, and the experience is strangely quaint -- considering you're on a sewage plant and are frequently slapped by the stench to remind you -- and often spectacular.

Built as part of his revolutionary London sewage system by Sir Joseph Bazalgette, a visionary Victorian engineer who was the Willy Wonka of this particular chocolate factory, the closer you get to it, the more you see not just the architectural pride at play, but loads of toilet humour too. Inside the old boiler rooms -- now a café and exhibition space -- I spoke to Mike Jones, acting chair of the trust, who told me more about Bazalgette's work. If you think London's filthy now, you should have been here in August 1858.

"It was called The Great Stink," says Jones. "It was reckoned that the Thames was about 20 per cent raw sewage." Oh God. "Basically, the flushing toilet was invented around 1795 and became very popular very quickly. Concurrently, London's population increased from about a million in 1800 to three million in 1850 and 6.7million by 1900. Cesspits would overflow into the tributaries and sewers, and the Thames became heavily polluted."

After an outcry led by scientist Michael Faraday, something had to be done. And Balgazette was tasked with sorting it out. His solution was to build a system of sewers that intercepted all the existing sewers and tributaries of the Thames to take all the waste east out to Crossness in the south and Abbey Mills in the north, where it would be released into the Thames. So they were still releasing raw sewage into the Thames, but down river enough for the tidal effect to take it out to sea. Still grim? Well, it saved tens of thousands of people from cholera, which was eradicated in the capital.

"The intriguing thing about Bazalgette was he thought we're only going to do this once, so let's get it right -- it was built for longevity, and his sewer system is still the backbone today." Indeed his system of dumping down river only began to change in the 1890s after the SS Princess Alice disaster -- 600 to 700 people died after the pleasure cruiser sank, many from asphyxiation because raw sewage had just been released into the same area -- when sludge boats took waste out into the North Sea to be released. That remained until 1998 when EU directives banned sea dumping, and now there's a sophisticated process of treatment.

Steven Elliot James

But anyway, the pumping station's role was to pump thesewageup from the sewers 30ft below for it to be released into the Thames. It remained in operation until the Forties. And the whole reason anybody is here in this place is that the engineering to achieve that is amazing.

The big deal here is entering the main pumping station to see a whole section restored to its original splendour. On the outside it's yellow Romanesque, but inside is dazzling neo-gothic Jules Verne Victorianism, in vivid green and red with decorative ironwork around its octagon centre. Ridley pointed out to me the witty touches of the ironwork, with figs and senna pod seeds -- natural laxatives -- and pretty white petals that are actually dogwood flowers, which were used at the time to prevent diarrhoea. Victorians: funny guys.

They have one engine restored of the original four so far, which they put to use on steaming days, and its these that are astonishing. Called rotative beam engines, they basically have these enormous 43ft beams, hooked up to 52-tonne flywheels -- they're big, built in the North and put together down here like giant Lego blocks. No wonder folk brave the smell to venture to this secret and unexpectedly awe-inspiring place.

Thames Water's new Tideway tunnel will open in 2025 and sit under the Thames to cope with storm water and ever-increasing sewage. It's a big deal, but you can't imagine they've done it with the flair and pride that was put into Crossness Pumping Station. Put simply: they don't make 'em like this any more.