some academics prefer to use the term donjon, and most modern historians warn against using the term "keep" simplistically. The fortifications that we would today call keeps did not necessarily form part of a unified medieval style, nor were they all used in a similar fashion during the period. History Timber keeps (9th–12th centuries) The earliest keeps were built as part of motte-and-bailey castles from the 10th century onwards – a combination of documentary and archaeological evidence places the first such castle, built at Vincy, in 979. These castles were initially built by the more powerful lords of Anjou in the late 10th and 11th centuries, in particular Fulk III and his son, Geoffrey II, who built a great number of them between 987 and 1060. William the Conqueror then introduced this form of castle into England when he invaded in 1066, and the design spread through south Wales as the Normans expanded up the valleys during the subsequent decades. In a motte-and-bailey design, a castle would include a mound called a motte, usually artificially constructed by piling up turf and soil, and a bailey, a lower walled enclosure. A keep and a protective wall would usually be built on top of the motte. Some protective walls around a keep would be large enough to have a wall-walk around them, and the outer walls of the motte and the wall-walk could be strengthened by filling in the gap between the wooden walls with earth and stones, allowing it to carry more weight – this was called a garillum. Smaller mottes could only support simple towers with room for a few soldiers, whilst larger mottes could be equipped with a much grander keep. Many wooden keeps were designed with a bretasche, a square structure that overhung from the upper floors of the building, enabling better defences and a more sturdy structural design. These wooden keeps could be protected by skins and hides to prevent them from being easily set alight during a siege. One contemporary account of these keeps comes from Jean de Colmieu around 1130, who described how the nobles of the Calais region would build "a mound of earth as high as they can and dig a ditch about it as wide and deep as possible. The space on top of the mound is enclosed by a palisade of very strong hewn logs, strengthened at intervals by as many