Under the Building Regulations all new and existing swimming pools, spas or other bodies of water of more than 300mm in depth (including those constructed prior to 8 April 1991) must have gates and doors installed with self closing and self latching devices (located at least 1.5m above ground level) that returns the door or gate to its closed and locked position at any point from a stationary start as failure to do so may incur a fine. Further information can be obtained from your local council.