The mind-expanding effects of a tipple relished by artists from ToulouseLautrec to Picasso - the aperitif absinthe, also known as the "Green Fairy" or "Green Muse" - have never been fully investigated.

The search for a scientific explanation has been hampered by the 1915 French decision to ban the drink as a dangerous drug - hallucinations and dementia were among the side-effects - making it difficult to obtain samples of the original concoction.