Brighton is known for its Victorian heritage, from seafront architecture to Magnus Volks’s wacky inventions. Something far less famous the Victorians left for us, though, lies beneath our feet: a remarkably intact network of 40-something miles of sewage tunnels this tour lets participants explore.

The walk begins with a mildly alarming emergency drill (in case of the real possibility of overflowing excrement waves) followed by a tacky-yet-informative DVD presentation.

The history of Sussex’s sewers is skimmed over, from how Dr Richard Russell’s promotion of sea-bathing’s health benefits led to the construction of a modern system, through to the present-day hi-tech cleansing facility at Black Rock.

Professionals from Southern Water offer a nice balance between technical knowledge and, erm, stuffed toy rats.

But the star of the show is always going to be the tunnels themselves. Once allowed into the city’s bowels (pardon the pun), it didn’t disappoint. Clad in helmets and head torches, walking down narrow passageways under Old Steine became an intrepid adventure.

Congealed fat resembled waxwork horrors beneath cavernous, intricately-carved corridors. Images of secret societies were conjured at every turn for the more excitable as the sensible ones marvelled at the sheer craftsmanship of some of Brighton’s real innovators.