Last month, I found myself wondering if it could ever be right to take a life, to end what appeared to be thousands of lives. It was after my annual reunion with two old college friends, at a newly opened hipster pie bar on the roof of a fashionable Dalston venue-cum-live-space, Pie In The Sky.

Danni had betrayed her Marxist roots to become a one-woman libertarian think tank, The College of Controversy; her counter-intuitive pronouncements are much in demand on late-night newspaper front-page analysis shows, thirsty for the illusion of balance; she ‘comes round’ to Jacob Rees-Mogg; she accuses a golden retriever bitch, that fostered an orphaned badger, of ‘virtue signalling’.

In the ’80s, Anna used to front an anarcho-feminist punk band, but last year, in a sleeveless summer dress, she collected an OBE for her work in public waste management, her now-shaven armpits reluctantly fragrant. “You’ve heard of the Monster Fatberg, the massive glob of grease and fat in the Whitechapel sewers?” she asked.

“Yes,” said Danni, “but I’m coming round to it. The Fatberg tells us nature won’t be corralled politely by civil engineers, and forces us to confront the filth that goes hand in hand with…”

“Danni,” Anna interrupted, “this is no time to provide off-the-peg contrariness to order. I need you both to see something.”

Ashen-faced, Anna took us by taxi to the corner of Castle Baynard Street and White Lion Hill, where the old city of London slides into the Thames in the shadow of St Paul’s, and where she, in her public health capacity, has a key to both the sewers and a subterranean store of wellingtons and waterproofs. “Take these,” she said, handing out clothes pegs, sick bags and nosegays.

Seven-hundred subterranean rat-infested yards of circular sewer stream later, lit by Anna’s flickering lamp light, we saw the fatberg, larger apparently even than the Whitechapel record breaker, its stench gagging us, its white mass glistening, somehow still off the media radar.

“You’ve hushed this one up, because it’s so embarrassingly big?” I asked.

“Hushed up, yes,” answered Anna, “but not because of its size. Listen.”

In the wet darkness we heard the murmurs, low rumbles of massed voices that seemed to emanate from the soggy body of the fatberg itself, mumbling overlapping sound-bites in all the accents of these isles: “Send them back.” “If they like being lesbians why don’t they go and live on Lesbos?”, “Political correctness gone mad.” “Most of them don’t even need their wheelchairs.” “He’s a laugh though, isn’t he, Boris?” “It was Adam and Eve not Adam and Steve.”

“Is it possible?” asked Anna. “It seems that all the bad energies of this landmass have taken some kind of physical form and drained down here to the edge of the Thames to collect in a sort of psychic sump. It’s like drivetime LBC given mass.”

I am not a religious person, but I am nonetheless a magnet for the supernatural, and was once sexually assaulted by the ghost of Napoleon in a French mausoleum. I found myself uncommonly attuned to the fatberg. “These voices – they’re not spirits,” I said, running my hand along the shining surface of the fatberg. “More like a sort of collective consciousness of current thinking that has found solid expression beneath the spiritual centre of the capital in this vast cluster of grease and fat.”

“I think it’s fabulous,” said Danni, by now almost prostrate on the sewer floor, “the distilled spirit of public opinion. As grain ferments into whisky, so this fatberg embodies the British public’s core values boiled down to essence.” And then, the fatberg’s monetisable qualities flashing across her indiscreet face, she said, “I must have it.”

“No Danni,” said Anna. “The authorities want it preserved. But I want to get rid of it. Now. I need you three to help me open the emergency floodgates and sluice it out to sea.”

And so half an hour later, the iron valves unlocked, we stood on a metal gantry over a Victorian brickwork ravine, the roar of water rushing beneath us, as the Opinion Fatberg shot in shattered pieces into the Thames. I found myself shuddering, as if a million voices cried out, and were silenced.

In the weeks since we obliterated the British Opinion Fatberg™, I have watched Danni’s tabloid newspaper columns go from strength to strength, their online shares growing by the million, as she achieves new levels of incoherent fury and prejudice. Acting on intuition, I contrived a reason to visit her in her Shoreditch flat.

When I went to the bathroom, a notepad and recording equipment were laid out by the sink. Pulling back the shower curtain I saw, oozing silently in its own washing up bowl, a mini-fatberg, muttering almost inaudibly about benefit cheats, evidently grown from a sample Danni must have secretly saved in the sewer.

“Isn’t it a marvel?” said Danni, sidling in to the room behind me, and handing me a glass of champagne. I had to admit that it was.