The dictionary defines a castle as any stronghold or fortified group of buildings; however, many purists, for example D. O'Neil who wrote the introductory guide to "Castles of England and Wales" published in 1954 by H.M.S.O. limit their definition to those strongholds erected since the Norman Conquest.

Castle building in Britain.

Aberbury Castle, Aberbury, Shropshire. South of the church.
This Welsh Marches castle has part of a tower and some bits of wall still standing.