R v GLADSTONE WILLIAMS
The Defendant is entitled to use such force as is reasonable in the circumstances as it appears to him, whether his belief is reasonable or not.
R v Gladstone Williams  3 All ER 411
A thief who robbed a woman in the street was apprehended by a bystander who caught him and knocked him down. The thief called for help, and a young man (who had not seen the start of the incident) intervened and hit the bystander in order to protect the thief from further beating.
At the Defendant’s trial on charges of assault causing actual bodily harm, the Recorder said that the Defendant’s mistaken belief that the bystander was acting unlawfully would be a defence only if it was reasonable. The Court of Appeal overruled this direction and said that any honest mistake would be sufficient. The reasonableness or unreasonableness of the Defendant's belief, said Lord Lane CJ, is material to the question whether the belief was held by the Defendant at all, but if the belief was in fact held its unreasonableness is irrelevant. The jury should be told that the prosecution has the burden of proving the unlawfulness of the Defendant's actions, and that if the Defendant was labouring under a mistake as to the facts he must be judged according to his mistaken view, whether or not on an objective view that mistake was reasonable.
Hence, the Court in R v Gladstone Williams held that the Defendant’s actions must be judged according to the facts as he honestly believed them to be. Self -defence can be used to protect oneself or another, or property from an actual attack or the threat of an imminent attack.
The social effect in requiring each citizen assisting another in peril might reduce the autonomy and privacy of others in pursuing their own objectives causing a rise in policing by citizens. Mistake and policing by a citizen were evident in R v Gladstone Williams , the appellant witnessed a man attacking a youth and intervened to aid the youth, however the youth had just committed a mugging and the attacker was trying to stop him from escaping. A Conventional view relies on defining legal duty with minimal liability which should only arise in certain cases. It does not oppose criminalising conduct to prevent inflicting harm on others. Williams approves that non feasance ought not amount to a crime even if the outcome is serious. Arguing the conventional view has been misinterpreted, Williams insists clarity and consistency must underpin court decisions having identified many inconsistencies. Williams recognises benefits of codification with the proviso of strict limitations. Smith identifies difficulties with a duty to care theory, accentuating the overlap between omissions and continuing act theory in Fagan. Smith argues the continuing act theory may have more effect than duty to act theory, implying there is no general theory that fits all situation.