APPENDIX R THE SO-CALLED SHELL KEEP

We have three accounts of motte-castles from the 12th century: that of Alexander Neckham, in the treatise De Utensilibus; that of Laurence of Durham, cited in Chapter VII., p. 147; and the well-known description of the castle of Marchem, also cited in Chapter VI., p. 88. All these three describe the top of the motte as surrounded by a wall (of course of wood), within which is built a wooden tower. The account of Marchem says that it was built in the middle of the area. This supports the conjecture in the text. Mr H. E. Malden has shown (Surrey Archæolog. Collections, xvi., 28) that the keep of Guildford is of later date than the stone wall round the top of the motte. Remove this tower, and there would be what is commonly called a shell keep. It would appear, therefore, that it was a common practice to change the bank or stockade round the top of the motte into a stone wall (no doubt as a defence against fire), leaving the keep inside still of wood. Four of the pictures from the Bayeux Tapestry (see Frontispiece) all give the idea of a wooden tower inside a stockade on a motte.