Class B - includes codeine, amphetamine, methylamphetamine, cannabis and cannabis resin, barbiturates and dihydrocodeine. Class C - includes mainly prescribed drugs such as tranquillisers. The most common offence is possession of a controlled drug. This includes joint possession of a common pool of drugs and past possession, when past drug use is admitted. By law, the police have to prove that you knew that you had the drugs on you.
More serious offences are supply and intent to supply.
It's important to remember that supply can also include selling or even giving drugs to a friend. If you are caught with drugs, saying that some are for a friend makes matter worse as you could also be convicted for supply. Cultivation of cannabis is also an offence with more severe penalties if there is intent to supply. The heaviest penalties under the law are for importing and exporting drugs. Some police forces always prosecute first time offenders with small amounts of drugs, while others are far more lenient, offering only a caution .