Police have the power to detain, for up to six hours, anyone suspected of having committed an offence punishable by imprisonment (including drugs offences). Police have the right to search anyone they suspect of possessing drugs.
Illegal drugs are widely available, especially in clubs. Cannabis possession is a criminal offence; punishment for carrying a small amount may be a warning, a fine or imprisonment. Dealers face stiffer penalties, as do people caught with other drugs.
On buses and trains (including the London Underground), people without a valid ticket are fined on the spot (£80, reduced to £40 if you pay within 21 days).