So, while John was pursuing his northward march, the barons sat still and waited. The southern division of John’s host meanwhile was far from idle. Between Christmas and the middle of January detachments of it overran the whole of Essex, Hertfordshire, Middlesex, Cambridgeshire and Huntingdonshire, while the main body marched to S. Edmund’s, drove the insurgents who had taken refuge there to seek another shelter in the Isle of Ely, followed them thither, and sacked, burned and ravaged the patrimony of S. Etheldreda as they did every other place to which they came.[1149] Their leaders, before setting out, had charged the constables of Windsor, Hertford and Berkhamsted to keep a watch upon all who went into and out of London, and if possible to stop the supplies of the barons there. This latter charge either proved impossible to execute, or the constables deemed its execution impolitic, and deliberately preferred to let the king’s enemies in London ruin themselves by “lying there like delicate women, anxiously considering what variety of food and drink could be set before them to renew their wearied appetites.”[1150] The advance of Savaric de Mauléon on Colchester, on January 29, perhaps roused them at last, for a report reached him that they were hastening to relieve it, and caused him to retire towards S. Edmunds,[1151] probably to rejoin the other royalist leaders who had been doing the work of destruction at Ely. But the barons, still vainly waiting for their foreign ally who came not, made no further movement; and even when the royalists fired a suburb of London itself, and carried off “plunder of inestimable value,”[1152] no retaliation seems to have been attempted. [Sidenote: 1215] While the barons slumbered--as a chronicler says--the king was not asleep;[1153] he was wreaking his long-delayed vengeance on the north. The malcontents in the land beyond the Humber had been quicker than their southern comrades to recognize their need of foreign help in their struggle against John, and they had taken a short and easy way of obtaining it for themselves. No sooner had civil war broken out in England in the autumn of 1215 than the young Scottish king, Alexander, who owed his throne and almost his life to the timely help which John had given to his father four years before, marched into Northumberland and laid siege, on October 19, to Norham castle. [Sidenote: 1215–16]