Wirral is a peninsula in the north-west of England. Its area is approximately one hundred square miles (260 sq km). It was a distinct administrative region at the time of the Domesday Survey in 1086 – it was listed as Wilaveston Hundred because the central village was Wilaveston (now Willaston).
Since the reorganisation of local government in 1974 the northern 60% of the peninsula has been administered as the Metropolitan Borough of Wirral, formed from the merger of the County Boroughs of Birkenhead and Wallasey, the Municipal Borough of Bebington and the Urban Districts of Wirral and Hoylake. From 1974 to 1986 the Borough was a district within the new county of Merseyside. Since 1986 it has been a standalone Unitary authority.
The southern 40% of the peninsula remained part of Cheshire, forming the administrative district of Ellesmere Port and Neston. In 2009 Cheshire was split in two and south Wirral is now administered as part of Cheshire West and Chester.
So - what is "Wirral"? It is the peninsula and it is also the smaller borough. Places such as Shotwick and Parkgate are on the peninsula but not in the borough. It is the responsibility of anyone writing about Wirral to be clear which definition they are using. Wirral History & Heritage Association refers itself to the peninsula unless specifically stated otherwise in some text.
There is now a third definition of Wirral. Royal Mail has decided that every address in the Borough of Wirral falls into one of four Post Towns - Prenton, Wallasey, Birkenhead and Wirral. Those definitions do not match any areas known to the residents. For Royal Mail, Claughton and Oxton are in Prenton; Heswall, West Kirby, Greasby, Egremont, New Brighton, etc. no longer exist; and Birkenhead is not in Wirral. Places that are not in Royal Mail's versions of Prenton, Wallasey or Birkenhead are stated to be in Wirral. Their confusing boundary names are based on their sorting and delivery offices, but are now officially part of a building's postal address.