 There are ten companies whose employees are sworn in as constables under section 79 of the Harbours, Docks, and Piers Clauses Act 1847.As a result, they have the full powers of a constable on any land owned by the harbour, dock, or port and at any place within one mile of any owned land.Additionally, there are also some forces created by specific legislation such as the Port of Tilbury Police (Port of London Act 1968).