...Titchmarsh, 65, asks in an ITV show to be screened on Christmas Day: "Is it edible?"
Professor Crawley replies: "That depends what you mean. It's eaten in some cultures for its hallucinogenic affects. But it also makes people who eat it very sick.
"The old-fashioned thing to do was to feed it to the village idiot, then drink his urine because you get all of the high without any of the sickness."
http://www.telegraph.co.uk/news/newstopics/howaboutthat/11289221/Queens-garden-at-Buckingham-Palace-contains-hallucinogenic-fungi.html