R v Waterfield [1963] 3 All E.R. 659 is an English Court of Appeal decision, a court of binding precedent, outlining the modern limits of the law that authorises a police officer to stop (and then conceivably detain) a person. This case produced what is known as the Waterfield test (incorporating the common law "ancillary power doctrine") for the limit of police authority to interfere with a person's liberty or property.