Urban Grimms.

One evening, not so long ago, a young woman who had just moved to London boarded a tube train late at night. There weren't that many people on the train so she found a seat easily and, becoming accustomed to London habits, she set about avoiding eye contact with all other passengers. But that same courtesy was not extended by the three people sat across the compartment from her.

Two serious looking men and, between them, a woman who stared fixedly and without facial expression, towards this story's protagonist. Who was, unsurprisingly, unnerved by this situation. Things got stranger still when, at the next station, a middle aged man boarded the train and immediately began conversing with our unnerved passenger before leaning towards her and whispering in her ear that if she knows what's good for her she will disembark the train at the next stop with him.

On arriving at the next station and seeing the platform was relatively busy, she did this, and as soon as the underground train pulled out the middle aged man informed the young woman that the staring woman was, in fact, dead and that there was a pair of scissors stuck in to the back of her head. The two men who appeared to be her friends were using the tube to dispose of a corpse.

There are eight million stories in the city. This is just one of them. If we'd waited to hear them all we'd still be there now but last night Scott Wood from the London Fortean Society (in collaboration with Gordon Rutter at the Edinburgh Fortean Society) took us on a brief tour through three of them:- The Corpse on the Tube (recounted above), The Helpful Terrorist, and The Hidden Insult.

Scott knows his stuff, he's written a book on the subject, so this was more than just a recounting of the stories. The free online talk, which Scott Zoomed into using an empty Bell pub in Whitechapel as his background just to remind us where we'd all like to be if we could right now, also delved into the very nature of urban legends, urban myths, and folklore and how the stories that go, for want of a better word, viral in the public imagination can often reveal our hidden prejudices, fears, and rational blind spots.

Urban legends can take the form of horror or ghost stories, and The Corpse on the Tube chilled me last night and again, today, writing about it, but they can also be revenge fantasies or stories that rely on an audience's shared reaction to that which they fear. Be it a rational fear of nuclear war or an irrational fear of foreigners or contracting AIDS.

Often there will be dirty jokes involved. Because British people, all people surely, love a dirty joke. Scott's tale began in the unlikely rural setting of Dorset where Agglestone Rock, or the Devil's Anvil, sits a few miles north of the seaside town of Swanage. Local folklore has it that it was thrown there, from The Needles on The Isle of Wight, by the devil. He'd been aiming to destroy, or at least damage, either Corfe Castle or Salisbury Cathedral (depending on who is recounting the tale) but the devil's aim was poor and his throwing arm, clearly, weaker than he imagined it to be.

It's folklore to explain something that science had yet to find an answer for. But when folklore is transported to cities like London, it becomes urban myth. The garish, and mostly unloved, Elephant and Castle shopping centre is soon to be demolished but some question why it was ever built in the first place. As it stands only a mile from the Houses of Parliament and was built at the height of the Cold War, it wasn't long before somebody put two and two together and came up with a number higher than four.

Obviously, the shopping centre was merely a front for the nuclear bunker that was being built beneath it to protect high ranking government ministers in the event of a nuclear war. The shopping centre was needed for cover as Russian spies would never be fooled otherwise. The theory of the nuclear bunker does not seem to concern itself with the fact that there is a large and busy tube station underneath the shopping centre but that's urban myths for you. They don't have to sound plausible, they only have to feel so.

People have claimed the story of the corpse on the tube is definitely true and, often, it is a sister's friend it has happened to but the fact that this story, and others, have cropped up in various iterations and various locations over time (this talk alone took us to Birmingham, Manchester, Sicily, New York, and Ohio) suggests that even if this did once happen for real, the myth, the legend, has now taken over.

The story of The Helpful Terrorist has taken an equally circuitous journey through time and space. You'll most likely be familiar with its most recent reboot. A friend tells of how a friend of theirs was shopping in Harrods when she noticed a man of Arabic appearance who finds himself a little short of cash when he reaches the till.

Feeling more flush than normal, she is in Harrods, she offers him £3 to complete his purchases and leaves the shop. Good deed done. But, soon the man is tapping on her shoulder, thanking her, and then solemnly warning her not to go on the tube that day. Interest piqued, she informs the local police who show her some photos of known, and wanted, terrorists and, you knew it, he's one of them.

He's trying to save her life because she helped him. While, at the same time, seemingly being quite indifferent to the lives of potentially thousands of innocent people. Local police stations don't even keep photo albums of wanted terrorists but why let that ruin a good story. Before the age of Islamist extremists, versions of the story were told where the helpful terrorist had a strong and soft Irish accent and before that, around the time of both World War I and World War II, the grateful shopper/murderous maniac would be German.

After 9/11, the story became so common that a joke version went viral. In this version events play out as above right until the end at which point the helpful terrorist warns our protagonist to stay away from Aberdeen Steak House on Piccadilly on Friday evening. "Why?", our hero asks, "will there be a bomb?". "No", comes the reply, "it's just very overpriced, really uncool, and their dessert section is very limited".

So as, presumably, not to upset still running restaurant chains, Scott changed the venue to the now defunct Pizzaland which, to me, didn't work quite as well. A small misstep in a talk that, once early tech gremlins were sidestepped, proved fascinating. The Hidden Insult, too, has many variations but almost all of them involve somebody taking revenge on someone for either a sleight, a perceived sleight, or simply for being too high and mighty.

Take, for example, the working class and Lewisham born, fashion designer Alexander McQueen who, before his untimely death at the age of forty in 2010, became so powerful in the world of fashion that when his shows were accompanied by freak weather, some suggested his tailoring skills were so otherworldly that they could summon clouds and winds.

That's an impressive pair of trousers. But not, perhaps, as impressive as a story about McQueen in his younger days. While apprenticing in Savile Row he found himself working on a suit for Prince Charles. Not having monarchist tendencies, McQueen is believed to have sewn the legend "I AM A CUNT" into the lining of the heir to the throne's whistle jacket.

Other versions have McQueen, more politely, marking his territory in Charles' outfits with "McQueen Was Here" or, if you're a fan of the Beano and the Dandy, "McQueen Woz Here", The royals seem to be prime candidates for these hidden insults as another story has a cheeky garage mechanic secreting pornography and swastikas inside the Queen and Prince Philip's Rolls-Royce.

There's a version of the tale in which Oasis buy a mixing desk from a Blur fan in Australia who, to rile the Gallaghers, has written Blur inside it for them to eventually find. The footballer Joe Cole is another assumed victim too. Cole had recently moved to Chelsea from their London rivals West Ham when he married fitness trainer and model Carly Zucker. Unbeknownst to him, the suit for his wedding day had been prepared by a disgruntled West Ham fan who hid West Ham's insignia, and the word Judas to boot, in its lining.

Even buildings can be used to carry hidden insults. When, in Victorian times, the architect Ernest Augustus Runtz, built a terracotta bank on Cornhill in the heart of the City of London, he found the building was beginning to impinge on space used by St Peter upon Cornhill, a 17c Christopher Wren church which is mentioned by Charles Dickens in Our Mutual Friend.

Requests to come to some kind of agreement on space sharing were firmly rebuffed by the church authorities and this so rankled Runtz that he decorated his bank with a host of malevolent demons. Satanic majesties that stared down, and across, to the church and unsettled the safe, conservative, Christian values of that institution.

I'm not sure how 'hidden' that insult is but it certainly isn't going anyway any time soon. There was a Q&A after the talk that took in Itzhak Perlman, black dogs, Slenderman, Little Red Riding Hood, and the phallic shadows that can be seen when the sun is low through the trefoils of Westminster Bridge and there were engaging, and thought-provoking, asides about what may be the stuff of future urban myths.

My favourite was the story of a grandmother arriving, in a driverless car, in the future, to see her grandchildren. Only she'd died en route and when the excited kids rushed out to see granny they got a very nasty surprise. Another, that has already started circulating, is the tale of a lady seen shopping in Fortnum & Mason at the exact same time she is at home dying in a fire.

Snopes is a handy website if you want to debunk these stories but Popbitch was a good one for spreading them. Rumours that take in the tale of protestors taking a dump into the 2012 London Olympic rings and Nicholas Hawksmoor using the obelisk spire he designed for John James' church of St Luke on Old Street to make a point about his critics.

In an age of mass, and weaponised, disinformation there is, of course, a danger in spreading untruths but a counterpoint to that is that it is human to tell stories. In fact it is one of the things that separates us from the lower beasts. We should continue telling stories, and I look forward to doing so over beer and curry again soon - when THIS is all over, but we should also continue questioning what agenda these stories serve. We should enjoy stories for what they are - stories. Or fables. Not necessarily truths. Thanks, as ever, to the London Fortean Society for a great evening.