A fungi expert intends to defy a ban stopping people from picking mushrooms on a huge estate in mid Wales.
Daniel Butler has been showing paying guests around the Elan Estate since 1998, and regularly picks fungus.
But the Elan Valley Trust, which is responsible for its flora and fauna, said this week that some species were in decline and imposed the ban.
The trust's chairman described Friday evening's free public foray as "extremely irresponsible".
Meanwhile, the Countryside Council for Wales (CCW) said picking small numbers of fungus was unlikely to jeopardise the species, but it was advisable to seek the permission of the landowner.
Mr Butler said: "I'm challenging the ban because it has no scientific basis and is unenforceable in practice.
"If an activity is harmless and has been carried on for centuries why ban it now? Today it may be mushrooms, but tomorrow it will be blackberries and sloes."
He explained that some mushrooms were so small that the only way to examine them was by picking them.
John Evans, chairman of the Elan Valley Trust, condemned Friday's foray.
"Whether or not his proposed actions are legal, in my opinion it is extremely irresponsible for him to encourage an unknown number of people to embark on a mass foray.
The Elan Valley is a special area of conservation
"However knowledgeable he may be personally about fungi, he cannot possibly instruct a mass of people on what they should or should not do."
The CCW said it was not a criminal offence to pick mushrooms growing in the wild.
A spokeswoman added: "While picking small amounts for your own use is often accepted custom, it is advisable, where possible, to seek the permission of the landowner.
"Picking a relatively small number of edible fungi in a responsible way is unlikely to jeopardise the presence of such fungi."
The estate's head ranger Peter Jennings said earlier this week that some people were "cashing in" by selling car boot loads of the mushrooms.
But Mr Jennings said there were no plans to erect warning signs on the 70 square mile (181.3 square km), 42,000-acre (16,997 hectares) estate which is in the counties of Powys and Ceredigion.