Police Act 1946
The Police Act 1946 (1946 c.46) was an Act of Parliament of the Parliament of the United Kingdom that provided for the amalgamation of smaller borough police forces with county constabularies in England and Wales, allowed for the merger of county forces in certain circumstances and changed the boundaries of the Metropolitan Police District. The appointed day for the amalgamations was 1 April 1947. On that date forty-five non-county borough police forces were merged with those of the counties in which they were situated. In the case of fourteen of these boroughs, they had already  been temporarily placed under the county police by the Defence (Amalgamation of Police Forces) Regulations 1942. Section 13 of the 1946 Act made these amalgamations permanent. One non-county borough force, Cambridge City Police, was allowed to continue, the city having a larger population than the surrounding county. The Act made similar provision for Peterborough City Police, although in the event it formed a combined force with the Soke of Peterborough. Following the 1947 mergers there were 133 police forces covering England and Wales: † The actual number was 53, as the Lincolnshire Constabulary was jointly maintained by three counties. Section  3 of the Act allowed for the voluntary amalgamation of county and county borough forces, while Section 4 gave the Home Secretary the power to make amalgamation schemes of constabularies. Section 16 provided for the "rectification" of the Metropolitan Police District, realigning it with contemporary local government boundaries. Section 18 placed the Isles of Scilly under the Cornwall County Constabulary Later amalgamations. The Home Secretary's powers under Section 4 of the Act were used on a number of occasions: