Collins v Wilcock  3 All ER 374:
A police officer was questioning a woman in relation to her alleged engagement in prostitution. The woman turned and walked away, and the police officer, without any lawful authority to do so, held her by the hand to prevent her from walking away. The woman in turn scratched the police officer to free herself from the police officer’s hold. An action for assault (which is battery in tort) was brought against the woman.
Whether the actions of the woman constituted battery.
The actions of the woman did not constitute battery.
Since the police officer had no lawful justification to restrain the woman according to the Street Offences Act 1959 c.57, the woman’s actions constituted a self-defence mechanism and cannot be held as assault. In addition, and owing to the lack of lawful justification, the police officer’s act of holding the woman’s arm was held to constitute battery.