On 4 March 1554 some hundreds of London schoolboys fought a mock battle on Finsbury Field outside the northern wall of the city. Boys have always gratified their innate romanticism by playing at war, yet this incident, organized between several schools, was overtly political and implicitly religious in character. It almost resulted in tragedy, and, though scarcely noticed by historians, it does not fail to throw Ught upon London society and opinion during a major crisis of Tudor history. The present essay aims to discuss the factual evidence and its sources; thereafter to clarify the broader context and significance of the affair by briefer reference to a few comparable events which marked the Reformation struggle elsewhere. The London battle relates closely to two events in the reign of Mary Tudor: her marriage with Philip of Spain and the dangerous Kentish rebellion led by the younger Sir Thomas Wyatt. The latter’s objectives were to seize the government, prevent the marriage, and, in all probability, to place the Princess Elizabeth on the throne as the figurehead of a Protestant regime in Church and State. While Wyatt himself showed few signs of evangelical piety, the notion of a merely political revolt can no longer be maintained. Professor Malcolm R. Thorp has recendy examined in detail the lives of all the numerous known leaders, and has proved that in almost every case they display clear records of Protestant conviction. It is, moreover, common knowledge that Kent, with its exceptionally large Protestant population, provided at this moment the best possible recruiting-area in England for an attack upon the Catholic government. Though the London militia treasonably went over to Wyatt, the magnates with their retinues and associates rallied around the legal sovereign. Denied boats and bridges near the capital, Wyatt finally crossed the Thames at Kingston, but then failed to enter London from the west. By 8 February 1554 his movement had collapsed, though his execution did not occur until 11 April.