Burning issues: The Fortean Times, purveyor of strange phenomena, hosts a 21st birthday convention this weekend. Serena Mackesy looks forward to it

A crematorium burns a human body in an hour and a half. Even so, the bones don't burn, and have to be ground in order to make that sandy stuff you get in urns.

When John Heymer, Gwent CID's Scenes of Crime Officer, was called to the home of one Henry Thomas in Ebbw Vale in 1980, the following scene greeted him: 'Between the armchair and the hearth lay a considerable amount of ashes. At one extreme end of ash lay a pair of human feet clothed in socks and attached to portions of lower legs.' Underneath the carpet on which the remains lay, the plastic floor tiles were undamaged; once washed, they showed no signs of anything having taken place on them at all.

John Heymer is convinced, in defiance of the scientific community, that spontaneous human combustion exists. He will be expounding his theories on Saturday at the University of London Union, when one of this country's finest publications, the Fortean Times, celebrates its 21st birthday with a conference, Unconvention 94.

The Fortean Times, the Journal of Strange Phenomena, is a magazine that inspires intense joy in its readers, a sizeable proportion of whom display few other recognisable signs of derangement. If you're familiar with Private Eye's 'Funny Old World' section, the front section of the publication, before the meaty articles kick in, is a bit like a 20-page version of that. Gleaning from newspaper reports worldwide, the magazine reports on anything, essentially, that is sufficiently weird or amusing: natural phenomena, religious stigmata, unknown fauna, coincidences, showers of frogs, obsessive behaviour. And, of course, there's Strange Deaths: did you hear that the chairman of Thames Water was found floating near Westminster Bridge in May last year? Or that Gerard Hommel, who had climbed Everest six times in the course of his life, died falling off a ladder?

Bob Rickard launched the FT with Paul Sieveking, 'like many fanzines' in 1973. 'It was bashed out on a typewriter, photocopied and sent out to friends and just grew from that.' Their inspiration was the writings of Charles Fort, a New Yorker who believed that scientists merely argue personal philosophies and discard, suppress or explain away phenomena that don't fit these. He was one of the first proponents of UFO theory, and published four books between 1919 and 1932.

Rickard and Sieveking, who temper the lunacy of what they do with a beguiling dryness, decided to continue his work and provide a forum for other people's theories and yarns, however far-fetched. These range from sightings of extinct animals to, in their classified ads section a few months back, an announcement from a man that he had 'proof that David Bowie is a space alien'. Now the journal has a circulation of 30,000. Two years ago they did a deal with John Brown, the publisher who took Viz to superstardom - 'in a way I think he probably saw in us the same sort of iconoclasm' - and the rest, as they say, will be history. Or at least, history as seen by those who regard time as a sequential series of events and not, for instance, a spiral or a blob or an inverted torus.

So, this weekend, roughly 1,000 people will converge on central London to hear talks and discussion on everything from shamanism to UFO abductions. It promises to be a riot.

Ralph Noyes will talk on psychic phenomena, spiritualist George Cranley will lecture on how mediums work, there will be a panel discussion on ghosts. On Sunday morning, one Doc Shiels will perform his play, Distant Humps, about the Loch Ness Monster, while on Saturday, Ian Rowland, of the Society of British sceptics, will stage a magic show.

Shoehorned into the midst of all this will be chat and updates on crop circles, urban folklore, cold fusion, cryptozoology, spinning discs, sea monsters, religious apparitions and ley lines: anything, basically, that most people don't believe in.

Sadly, however, Mary Seal, who was to give a talk on conspiracy theories, has pulled out. Maybe she thought it was a set-up.

Unconvention 94, 10.30am-6.30pm, 18 and 19 June, the University of London Union, Malet St, London W1, pounds 15 day ticket, pounds 20 weekend. Some tickets will be available on the door; call 0373 451777 to book in advance. The Fortean Times is available bi-monthly from many newsagents

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