To resume. The external or written evidence is as follows. On the one hand, we have the clear and positive statement of a contemporary writer, Robert du Mont, that Henry I. built this keep in 1123. On the other, we have no statement from any contemporary that it was built by William of Arques (in 1039-1043). He is merely credited with founding the _castellum_, and in none of the contemporary accounts of its blockade and capture by his nephew is there any mention of a _turris_. The distinction between a _castellum_ and a _turris_, with their respective independence, has not, as I have shown, hitherto been realized, and it is quite in the spirit of older students that M. Deville confidently exclaims— "Or, conçoit-on un château-fort sans murailles? Un château-fort sans donjon, dans le cours du XIᵉ siècle, en Normandie, n'est guère plus rationnel" (p. 310). As to the "murailles," Mr. Clark has taught us that palisades were not replaced by walls till a good deal later than has been usually supposed; and as to the "donjon," if, as I have established, so important a fortress as Rochester was without a keep in the eleventh, and indeed well into the twelfth century, other _castella_ must have been similarly destitute—probably, for instance, Newcastle, as we have seen, and certainly Exeter, of which Mr. Clark writes: "There is no evidence of a keep, nor, at so great a height, was any needed" (_M. M. A._, ii. 47). The same argument from strength of position would _à fortiori_ apply to Arques, and there is, in short, no reason for doubting that the _castrum_ of William of Arques need not have included a _turris_.[1003]