It is not easy to arrive at a satisfactory calculation of the approximate population of London at different periods. At the end of the twelfth century Peter of Blois, Archdeacon of London, in a letter to Pope Innocent III., calculates the population at 40,000, and this is a quite probable calculation, although Francis Drake maintains that London was less populous than York about the time of the Conquest. York, however, could not then have had anything like 10,000 inhabitants. Fitz-Stephen greatly exaggerated the population of London. He wrote: 'The city is ennobled by her men, graced by her arms, and peopled by a multitude of inhabitants, so that in the wars under King Stephen there went out to a muster of armed horsemen, esteemed fit for war, twenty thousand, and of infantry sixty thousand.' Hallam agrees generally with Peter of Blois' calculation, for he supposes London to have had a population in John's reign of at least 30,000 or 40,000. In 1377 the population, reckoned by the poll tax, was 44,770; the number taxed (consisting of males and females above fourteen years of age) being 23,314. We see from these numbers how greatly the population of London was in excess of the other great towns. From the same source we find the population of the towns next in size were:-- York, 7248 Bristol, 6345 Plymouth, 4837 Coventry, 4817 Norwich, 3952 Londoners were fortunate in not having suffered from any severe attack upon their fortifications, and therefore we are unable to tell how London would have stood a prolonged siege. We know, however, that at some periods it was very insecure. The most portentous event in England during the Middle Ages in respect to the changed conditions of life caused by it was the Peasants' Rising of 1381, the turning-point of which is entirely connected with the history of London. For four days the very existence of the city was in the direst peril. It is styled a rising, but it was really a revolution, and it is only lately that the full history of the movement has been presented to us in Mr. G. M. Trevelyan's valuable book, _England in the Age of Wycliffe_ (1899). There are two particular incidents in the history of mediæval London which are of the first importance as illustrations of the life of the inhabitants of a walled city. They stand alone, for no other internal occurrences fraught with such possible evil consequences are to be found in our history; and it is well to compare their likenesses and distinguish their unlikenesses. For this purpose it is not necessary to enter at all fully into the respective causes and effects of Wat Tyler's and Jack Cade's Rebellions. The consideration of these points belongs to the history of the country, but a fairly full account of the proceedings of the few days in which the city was given over to the lawless violence of the followers of Wat Tyler and Jack Cade respectively seems to be necessary here.