I’m not sure I’ve walked into a room full of excrement before. Five slabs of faecal matter, arranged under mood lighting like some scatological Take That tribute act. Very strange. Such is the wont of the Wellcome Collection, which habitually lines its galleries with unlikely wonders.

I’m walking around their new exhibition Dirt. It opens to the public today, and is their best show for a while. The sculpted rhomboids of poo are the least of it.

Dirt might seem a rather limiting theme, but the curators insist they had the opposite problem. As they sat down to plan the exhibition, they discovered that just about everything on earth has some connection to dirt.

To try and build in some kind of focus, the show is split into six zones — like a feculent version of the Crystal Maze. The most interesting, to me at least, was the section on London’s grimy history. You can probably guess most of the content. The Great Stink, Bazelgette’s sewers, and the oft-told story of John Snow’s cholera investigations are all given prominent billing. You might not have been aware, however, that Nature’s London offices were built right next door to this mountainous pile of Victorian crap.

It’s pretty much where King’s Cross Station sits today. Some of the dust was used to make the bricks that went into the station. The rest was transported to Moscow to help rebuild the city after a war. Remarkable.

Elsewhere in the exhibition, you’ll find ideas as diverse as Nazi racial purification, 18th Century Dutch cleanliness, early antiseptics, micrographs of bacteria and the conversion of the world’s largest landfill (on Staten Island, since you ask) into a giant park.

As you’d expect, the exhibition is supported by a long series of events. Check out the programme here.

Dirt at Wellcome Collection runs until 31 August and entrance is free.