via wiki: The Royal Society of London for Improving Natural Knowledge, commonly known as the Royal Society, is a learned society for science, and is possibly the oldest such society still in existence. Founded in November 1660, it was granted a Royal Charter by King Charles II as the "Royal Society of London". The Society today acts as a scientific advisor to the British government, receiving a parliamentary grant-in-aid. The Society acts as the UK's Academy of Sciences, and funds research fellowships and scientific start-up companies.

Robert Hooke, a contemporary of Isaac Newton, was also the curator or experiments for The Royal Society. In 1681 he made friends with a sea captain and writer named Robert Knox. From Knox's sea voyages for the East India Company, he had come into possession of "India Hemp" or ganja.

Knox introduced Hooke to the herb, and in 1689, Hooke recommended it to members of the Royal Society for its curative properties - and said the worst side effect was laughter.

William Brooke O'Shaughnessy, who began work shortly before Queen Vic took the throne, is credited with bringing cannabis medicine to Great Britain, after a stint working in India and experimenting with cannabis and observing its use among the population there at the time.

This is probably in the article - but it's a reality that cannabis was part of medical life until it was made illegal in the 1930s. It wasn't until Mexicans began settling in California that it suddenly became the subject of "reefer madness."