I think Druidic mushroom usage is assumed/suspected
but as someone whose dissertation was on pre-Roman British religion I can say with some certainty thet there is no written or archaeological evidence. Our entire knowledge of Druidic religion comes from a few lines of text only - most of them by Julius Caesar in his 'Britannia'. This makes a mockery of so-called modern day Druids whose entire 'religion' dates back no further than the mid-C19th.
( Monty Boyce, My cheese game is strong, Mon 28 Mar 2011, 17:33, 1 reply, 15 years ago)

You're not telling me that cunt King Arthur and his fellow Stonehenge 'druids' is a bullshitting makeup artist, well I never
Perhaps he should go back to drinking special brew down Holloway Road. I believe the Romans took particular umbrage with the Celts practice of human sacrifice, which is a bit odd considering their own savage practices. Tarpeian Rock anyone...
( Light In Chains maker of the ikea sofa, Mon 28 Mar 2011, 17:41, Reply)

Quite so.
They were hypocrites of the first water on many levels.
( Monty Boyce, My cheese game is strong, Mon 28 Mar 2011, 17:45, Reply)