What is a Caution? What happens if I am not cautioned by the police?

Under the Police and Criminal Evidence Act the police must caution anyone they reasonably suspect of having committed a criminal offence before questioning them. Under the Act, the associated codes and the case law associated with it failure to administer a caution in circumstances where it should have been administered means that all answers to questions that follow are inadmissible against a defendant and cannot be used in Court proceedings against them.