The Danes overran this part of England more than once, and the camp at Danesbury was probably their work. Also, they are thought to have had a camp upon Port Hill, of which, however, it is said that no traces are now to be seen. It was upon the river Lea, between Hertford and Waltham, that Alfred rendered the Danish fleet useless by blocking up the river, and so preventing their return. It is on record that this was effected, not by actually throwing a dam across the stream, but by the far more scientific process of cutting a number of channels for its waters, each too shallow to allow the vessels to float down. By this means the retreat of the Danes to the Thames was cut off, and they were fain to march inland to the Severn at Bridgenorth. In 913 the protection afforded by the Hertford Burhs seems to have attracted inhabitants, who occupied both banks of the river Lea, and the town thus situate was raised by Edward into a royal Burgh, held of the Crown by burgage tenure. Hertford was so held of the Confessor, and so accepted by the Conqueror, and entered in Domesday, which, however, as was not uncommon, makes no mention of the castle, nor, indeed, of the churches. William is said to have strengthened the castle, and he gave it in charge to Peter de Valoignes, one of his followers, who transmitted it to his son Roger, and he to his two sons in succession, Peter and Robert. The male line closed with Robert, whose daughter and heiress, Gunnora de Valoignes, married Robert Fitz-Walter. The charge of the castle does not seem to have descended, but to have been resumed, possibly as a male fief, by the Crown. King John, that most erratic of monarchs, held the castle, and visited it in 1212, 1213, and 1216. In this latter year, however, it was attacked by Lewis of France, who laid siege to it from St. Martin’s (November 11) to St. Nicholas’s Day (December 6), and finally took it. Robert Fitz-Walter, an adherent of Lewis, took the opportunity to revive his wife’s claim, but without success. It was finally recovered by John, and transmitted to his son Henry III., who placed Richard de Argentin in charge of it, and expended £20, and probably other sums, in its repairs. In 1226 it was held by Hubert de Burgh, on whose fall Henry granted it to be held _in capite_ by William de Valence, after whom it was held by his son, Aymer, Earl of Pembroke.