instruction: According to this paragraph, what was the most common type of castle in England following the Norman Conquest?
context: There are nine castles in Greater Manchester, a metropolitan county in North West England. They consist of four motte-and-bailey castles, three fortified manor houses, an enclosure castle, and a possible shell keep. A motte-and-bailey castle is characterised by two elements: the motte is an artificial mound with a wooden stockade and stronghold on top, usually a stone keep or tower, while the bailey is a defended enclosure adjacent to the motte, typically enclosed by a ditch and a bank topped by a timber palisade or stone wall. Motte-and-bailey castles were the most common type of castle in England following the Norman Conquest. A shell keep was a motte with a stone wall rather than a wooden stockade on top; there would have been no tower within the walls. Four of Greater Manchester's castles are scheduled monuments: Buckton, Bury, Radcliffe Tower, and Watch Hill. A scheduled monument is a "nationally important" archaeological site or historic building, given protection against unauthorised change.
response: According to this text, the Motte-and-bailey castles were the most common following the Norman Conquest.