From Wikipedia

Britain's Most Dangerous Drug

The Misuse of Drugs Act 1971 is an Act of Parliament that forms the central piece of legislation around the United Kingdom's drug policy is built.

The Act sets out three separate categories, Class A, Class B, and Class C. Class A drugs represent those that the British Government has deemed most dangerous, and so carry the harshest punishments. Class C represents those thought to have the least capacity to harm, and so the Act demands more lenient punishment. Being found in possession of a drug on this list is dealt with less seriously than would be if it were deemed that there is intent to sell the drug on to others. Possession with intent to supply carries a maximum penalty of life imprisonment. Punishment, however, is increasingly being seen as outdated, and the Government is gradually working towards a focus on harm reduction instead.

Substances may be removed and added to different parts of the schedule by statutory instrument, provided a report of the Advisory Council on the Misuse of Drugs has been commissioned and has reached a conclusion, although the Secretary of State is not bound by the council's findings. This list has in practice modified a great number of times, sometimes removing substances, but more commonly adding some; for example, many benzodiazepines became Class C drugs in 1985.

Glossary of terminology

anabolic steroids — hormones that build muscle tissue
benzodiazepines — sedatives with calming properties
cannabinoids — drugs that bind to cannabinoid receptors
hallucinogens — drugs that alter perception of reality
opioids — sedatives that relieve pain (but are highly addictive)
phenethylamines — hallucinogens based on phenethylamine
sedatives — drugs that lower consciousness
stimulants — drugs that heighten consciousness
tryptamines — hallucinogens based on tryptamine