'Superior herb' was given royal approval

As early as 2737BC the Chinese Emperor Sheng Nun described cannabis as a superior herb, and for centuries it was embraced unreservedly. The Roman emperor Nero's surgeon praised it for its medicinal efficacy. In 1794 George Washington urged his gardener to "sow it everywhere". Queen Victoria took it for her period pains. In 1901 a Royal Commission concluded that cannabis was relatively harmless and not worth banning.

As early as 2737BC the Chinese Emperor Sheng Nun described cannabis as a superior herb, and for centuries it was embraced unreservedly. The Roman emperor Nero's surgeon praised it for its medicinal efficacy. In 1794 George Washington urged his gardener to "sow it everywhere". Queen Victoria took it for her period pains. In 1901 a Royal Commission concluded that cannabis was relatively harmless and not worth banning.

An Irish doctor working in Calcutta in the 1930s was the first Westerner to recognise the drug's ability to alleviate various conditions, including epilepsy and rheumatism.

The recreational use of cannabis led to its prohibition in the 1928 Dangerous Drugs Act, and the Sixties were marked by high-profile protests against the law. In 1967, a full-page advertisement in The Times - signatories included the Beatles and the novelist Graham Greene - called the law immoral and unworkable. There were also "smoke-ins" in Hyde Park. However, in 1968, the Labour government rejected the investigative committee's conclusion that "consumption of cannabis in moderation has no harmful effects".

Pressure for legal change gathered pace again in the 1990s. In 1997, the Alliance for Cannabis Therapeutics (ACT) launched a national advertising campaign urging legalisation for medical uses. The following year, thousands marched on Trafalgar Square to back The Independent on Sunday's campaign for decriminalisation.

Tony Blair has supported the use of cannabis for medicinal purposes. However, his government has this year rejected recommendations from the Police Foundation that certain drugs should be reclassified and penalties reduced.