On the morning after the May Bank holiday in 1994 a young Romanian chemistry student called Ioana

On the morning after the May Bank holiday in 1994, a young Romanian chemistry student called Ioana Popa returned to her laboratory bench at Bradford University. She had just spent the weekend in Germany and was quite unprepared for what she was to find. By chance, something had happened to her experimental materials which could prove to be a decisive factor in the war against cancer. Dr Popa was working on a toxic chemical extracted from a wood-rotting fungus. For her research she needed to use the drug Tamoxifen, used to control breast cancer.

Tamoxifen is made up of two forms, a Z form - the important one - and an E form, which is thought to cause endometrial cancer. Ioana Popa left a flask containing an oily mixture of Tamoxifen and her fungal chemical on her bench and expected to find everything as she had left it. But something happened in her absence."When I got back from Germany, I found beautiful white crystals at the bottom of the flask," she says. At first she was at a loss as to what to make of the crystals. An analysis demonstrated that the flask contained a pure form of Z-Tamoxifen, quite devoid of any E-Tamoxifen.

It was an "accidental" breakthrough which looks as if it could lead to a new approach to treating cancer. The head of Clinical Oncology at the university, Professor John Double, goes as far as to suggest that the finding is a "penicillin-type discovery", a reference to the chance finding by Alexander Fleming of the penicillin fungus, which had made a home in a discarded petri dish.Dr Popa's serendipitous production of the crystals is not the end of the story, nor is it anywhere near the beginning; rather it was the lynchpin in a change of events that involved forays for fly agaric toadstools and other fungi in woodlands from Britain to Malaysia.The story began in 1953 when Ray Edwards, now a Bradford University scientist, was a young student of organic chemistry. At that time, the "natural" production of chemicals was in vogue. In the woods around Bradford, he gathered toadstools, such as the brilliant red and white spotted fly agaric, and examined the caps of these fungi for their chemical composition. Earlier, in the Thirties, an academic called Fritz Kögl had already described the chemical structure of the coloured pigments produced by the fly agaric, but Dr Edwards thought this assessment was wrong.

He eventually proved that Dr Kögl was incorrect.By then what had begun as an academic puzzle and a fashionable topic to gain a PhD had turned into a passion. He next looked at the Boletus species, a type of fungus whose flesh turns blue when bruised; it took him six years to crack the structure of their unique pigment. However, even in this rarefied field, Dr Edwards had a competitor, a German called Wolfgang Steglich. It became a race between them, but one that Dr Edwards could not hope to win.The woods that surrounded Bradford were rapidly dwindling, and so were the toadstools.

Dr Edwards ventured further afield, down to the south of England to places such as Windsor But Dr Steglich had a major advantage: the Black Forest. This famous wood, which extends for over 90 miles along the Rhine valley, was right on his doorstep. Dr Steglich would always have easy access to far more fungi than Dr Edwards could ever hope to collect.Dr Edwards faced a dilemma; he was losing the battle, but did not want to give up the fight. So he teamed up with Professor Tony Whalley, now at John Moores University in Liverpool. Professor Whalley was the perfect partner: not only did he collect and identift fungi from around the world, but he was prepared to give samples to Dr Edwards so that he could culture them in the lab. Moreover, Professor Whalley had the advantage of having researched one of the most widely distributed and common families of fungi, but one about which the least was known.Professor Whalley's pet fungi was the Xylariaceae, a wood-rotting fungus that grows on trees, but can also flourish on other plants, in the soil and even in insects. It is found in places as far apart as the rainforests of Malaysia and the alder groves of middle England.