Taken from BASC website .
The Wildlife and Countryside Act 1981 amended Section 6 of the Ground Game Act and Section 50 of The Agricultural (Scotland) Act 1948, to allow night shooting of ground game under certain conditions.
England and Wales: it is lawful for the occupier of any land himself, or one other person authorised by him, to use firearms for the purpose of killing ground game at night if the occupier has the written authority of a person entitled to kill or take the ground game on their land e.g. holder of shooting rights.