A battery is the application of force to another person.
A battery does not always presuppose an assault, even though they usually go hand in hand. For example, you threaten somebody (assault) and then you hit them (battery).
The merest touch could be a battery (Collins v Wilcock), if this touch was avoidable in our normal day to day lives. In some situations, say on a train, we all agree to being touched at some point because of its expected cramp conditions; this is called implied consent, however if a man touched the bottom of a womans skirt without permission then this could be a battery.
Is there a requirement of hostility?
In Faulkner v Talbot 1981, Lord Lane said…