R v LAMB
The Defendant must make the victim feel that he can and will carry out threat of force. There is no assault whether it is obvious that the Defendant cannot actually use force.
R v Lamb  2 All ER 1282
The Defendant and his friend were playing with a revolver. In the chamber there were two bullets, but neither was opposite the hammer when the Defendant, in jest, pointed the gun at his friend and pulled the trigger. The chamber rotated and the friend was killed.
The Court of Appeal said that since the victim shared in the joke, consented to having the gun pointed at him and did not feel threatened (since both believed the gun to be safe at that time) there was no assault and hence no unlawful act on which a charge of manslaughter could be sustained.
The Defendant was not convicted since the element of apprehension of personal violence could not be sustained. Since the victim, at whom the pistol was pointing, did not fear the probable infliction of violence because he did not think the gun, with which they were playing, would fire, there was no indication that any kind of attack had taken place. (there was also no instance of assault since the defendant lacked the essential mens rea).
The defendant is required to do some action that puts the victim in a state of reasonable apprehension (that is, belief) that he will be subjected to imminent and unlawful physical violence. In order for the offence to have been committed, it is not necessary for the defendant to have actually made physical contact with the victim or used force. It would be necessary for him to only utter a few words or make a few physical movements (such extending his fist towards the victim), which would lead the victim to believe that he is going to be hit.
From the above definition we can identify that the necessary actus reus of assault consists of the accused performing actions pertaining to causing the victim to ‘apprehend immediate unlawful violence’. This can be seen in R v Lamb  where it was decided that the defendant, who had recklessly killed the victim, was not guilty of assault due to the victim not perceiving that the firearm that killed him was in fact loaded. Moreover, the threat of violence must be unlawful and this is satisfied as she had said “I’m going to kill you, you whore”. The threat is also immediate. Barbara must believe that immediate violence will be inflicted upon her, and we can say there is an element of ‘immediacy’.