"This is called the Brown Roll Rim and eating it will kill you – eventually your red blood cells will disintegrate and you will start to bleed from your eyes and mouth."

It was a sobering thought for a sunny autumn morning, taken in by the hushed group of intrepid foragers I'd joined for a day of mushroom picking with River Cottage's John Wright.

"This one is poisonous – or a useful laxative, depending on how you look at it," he explained matter-of-factly of another find, before saying a third specimen would make you sweat profusely and then induce an intense chemical "high".

"God, they sound like effects from Doctor Who," piped up a fellow hunter, trying to break the ice as we looked at one another in an increased state of alarm.

We were in woodland in Bells Yew Green – not in the savage wilderness of the Amazon Forest – and within five minutes had stumbled across a plethora of provisions that could kill, maim or get us locked up for several years for possession of Class A drugs.

"That's the thing with mushrooms, if you're nervous and not sure what you're looking at, then be afraid," warned Wright, as he handed out baskets for our edible and inedible discoveries.

My knowledge of mushrooms prior to the fungal foray day paled in comparison to Wright's – a field mycologist of 30 years who wrote a book on the topic for chef Hugh Fearnley Whittingstall's River Cottage – and who reeled their Latin names off his tongue as fluently as I recite the alphabet.

Despite picking over the years in the South West of England and in Spain, where I make an annual foraging trip accompanying my Spanish father and uncle, I've only ever hunted for one particular kind. Last year my uncle threw a wicker basket full of my finds back into the woods because they weren't the specific Ceps he wanted to sell in his restaurant in Monovar, Alicante.

So to be faced with such a bewildering array which could whet my appetite or massacre my intestine, in under a square mile, was overwhelming.

It was also confusing – we'd find a "quite tasty" one but then, alongside, would be an apparently identical specimen that would, when digested, treat you to a horrendous bout of diarrhoea.

Some smelt of coconut, others of radishes and one couldn't be eaten if you'd drunk alcohol – while a taste test proved a tiny slice of a milk cap on your tongue will heat it up like a chilli.

And they grew wherever they fancied – beside a battered caravan in a rubble-strewn courtyard, on horse dung (thankfully you couldn't eat those) and next to tatty iron fencing.

Strolling through the trees, the talk turned to magic mushrooms after the discovery of the "sweat and high" toadstool.

"I've had magic mushrooms three times and that was enough," said Wright of the fungus which is now illegal to pick unless you have no idea what it is.

"Just after the changing of the law, I took some people out on a foray and told one man 'there's some toadstools down there, why don't you pick them?'

"With his hands full, I then told him he was stood with a handful of Class A drugs which, if he'd known what they were, could get him a few years in prison. He looked very embarrassed… before admitting he was a policeman!"

Two thirds of our way into the three-hour foray, which culminated with a three-course meal back at Moon Down's HQ, fellow forager Simon Burford, 25, of Tunbridge Wells, pointed out the basket of inedibles was decidedly fuller than the edible one.

The problem was rain – or a distinct lack of it – and Wright must have been the only person praying for the wet stuff as Britain basked in glorious sunshine last month, because the dry patch had led to a dearth of fungi.

"It looks like we might go hungry," Mr Burford said, before cheerfully admitting the course would make him more confident in scouring his local woodland, having previously been reluctant to cook what he found.

Mother-of-two and forager Emily Best, 32, of Southborough, who brought along nine-week-old daughter Mabel for the day, also believed she would now be more adventurous in her pickings.

"Normally we go on walks and take everything home, take a picture of what we've found and put it in the bin. At least now we'll be able to pick up a few more things and know they're OK."

I wished I could share their optimism. But after hearing of Horse Whisperer author Nicholas Evans, his wife and brother-in-law who suffered kidney failure after eating the wrong fungi in Scotland, I started to wonder if I'd ever eat a mushroom again.

Every time I thought I understood what was safe to eat, a spanner was thrown into the works.

"It might look similar, but it's not. Some people will eat it, but it could give you problems," Wright would point out.

During a three-course meal, which thankfully only relied on some of our finds to beef up a delicious mushroom risotto, we came up with a foolproof way to help us in our hunting.

We'd build a smartphone App so foragers could send snaps of finds to a mycologist, who could instantly say if it was edible.

But the idea seemed fanciful, even more so with John's light-hearted assertion that most of the serious mycological taxonomists were "grumpy and very competitive", so it was with eternal gratitude that during the Q&A session about our 41 discoveries it was asked what would be the safest mushroom for us to pick.

"That's easy and I wish we'd seen one today," said John as he thumbed through a battered book looking for a photograph.

"The hedgehog mushroom doesn't really look like anything else, normally grows in beech or spruce woods and I've only ever been told of one side effect, which I don't think is a problem – a female friend once said she couldn't eat them because it made her breasts swell."

So although I couldn't tell you its Latin name, or even what it looks like – it seems I've finally found my mushroom to look out for. I'll still keep John's number in my phone just in case, though.

Another foraging foray with John Wright is being held in 2012. Visit www.moondown.co.uk