Of course whenever a motte was thrown up, the first castle upon it must have been a wooden one. A stone keep could not be placed on loose soil.[215] The motte, therefore, must always represent the oldest castle. But there is no reason to think that the motte and its wooden keep were merely temporary expedients, intended always to be replaced as soon as possible by stone buildings. Even after stone castles had been fully developed, wood continued to hold its ground as a solid building material until a very late period.[216] And mottes were used not only throughout the 11th and 12th centuries, but even as late as the 13th. King John built many castles of this type in Ireland; and as late as 1242 Henry III. ordered a motte and wooden castle to be built in the island of Rhé.[217] Muratori gives a much later instance: in 1320 Can Grande caused a great motte to be built near Pavia, and surrounded with a ditch and hedge, in order to build a castle on it.[218] And as will be seen in the next chapter, there is considerable evidence that many mottes in England which were set up in the reign of William I., retained their wooden towers or stockades even till as late as the reign of Edward I. The motte at Drogheda held out some time against Cromwell, and is spoken of by him as a very strong place, having a good graft (ditch) and strongly palisaded.[219] Tickhill Castle in Yorkshire had a palisade on the counterscarp of the ditch when it was taken by Cromwell.[220] The position of these motte-castles is wholly different from that of prehistoric fortresses. They are almost invariably placed in the arable country, and as a rule not in isolated situations, but in the immediate neighbourhood of towns or villages. It is rare indeed to find a motte-castle in a wild, mountainous situation in England. The only instance which occurs to the writer is that of the motte on the top of the Hereford Beacon; but there is great probability that this was a post fortified by the Bishop of Hereford in the 13th century to protect his game from the Earl of Gloucester. Nothing pointing to a prehistoric origin was found in this motte when it was excavated by Mr Hilton Price,[221] though the camp in which it is placed is supposed to be prehistoric.