Battery is provided under common law. However s39 of the Criminal Justice Act 1988 mentions the fact that it is a summary offence and that it has a fixed term sentence of 6months.
The actus reus of battery is: Application of unlawful force
In Collins v Wilcock: lord Goff said an unwanted touch can technically amount to unlawful force. This was confirmed in Thomas.
Thomas said this includes the slightest of touch
Lord Goff also said, however that everyday jostling is inevitable but 'no greater degree of contact than that necessary should be used'.If degree of contact is used than necessary, then that can be unlawful force.
A battery may be indirect ( where the D doesn't not aim to touch the V).This was illustrated in DPP v K and Haystead.
The force has to be 'unlawful'. It may be lawful if the V consents.
The mens rea of battery is: Intention or recklessness as to the application of unlawful force (Savage)