William skirted the dense forest of Andredeswealde, and, striking the main road at Canterbury, progressed to Southwark, which he destroyed. Now, good soldier and wise man that he was, William saw that a definite attack on London would be a difficult matter, and would profit him nothing. So he set to work to do what others had done before him—to cut off the city from its supplies. Marching westwards, he made his way to the crossing at Wallingford, and there reached the north bank of the River. Striking north-east again, he came soon to Watling Street once more, and thus cut off all the northern trade. London was in this way cut off from practically the bulk of its supplies; and the citizens were glad to make terms before worse things happened. Probably the surrender occurred sooner than it might otherwise have done, by reason of the exceedingly mixed nature of the population. London counted among its citizens, as we can tell by reference to the documents of the time, merchants from many different parts of France—Caen and Rouen in particular—and from Flanders and Germany. William kept loyally to the promises which he had made in the treaty, maintaining the rights of the city, and seeing that the thirty or forty thousand citizens had the proper protection he guaranteed. True, he built the great threatening Tower of London, about which we shall read in another chapter, but it is very probable that even in that the citizens saw only a strengthening of the old bastions built in former days for the guarding of the city.