The reign of Edward I (1272–1307) was rather more successful. Edward enacted numerous laws strengthening the powers of his government, and he summoned the first officially sanctioned Parliaments of England (such as his Model Parliament). He conquered Wales and attempted to use a succession dispute to gain control of the Kingdom of Scotland, though this developed into a costly and drawn-out military campaign.

His son, Edward II, proved a disaster. He spent most of his reign trying in vain to control the nobility, who in return showed continual hostility to him. Meanwhile, the Scottish leader Robert Bruce began retaking all the territory conquered by Edward I. In 1314, the English army was disastrously defeated by the Scots at the Battle of Bannockburn. Edward's downfall came in 1326 when his wife, Queen Isabella, travelled to her native France and, with her lover Roger Mortimer, invaded England. Despite their tiny force, they quickly rallied support for their cause. The king fled London, and his companion since Piers Gaveston's death, Hugh Despenser, was publicly tried and executed. Edward was captured, charged with breaking his coronation oath, deposed and imprisoned in Gloucestershire until he was murdered some time in the autumn of 1327, presumably by agents of Isabella and Mortimer.

In 1315-1317, the Great Famine may have resulted in half a million deaths in England due to hunger and disease, more than 10 per cent of the population.

Edward III, son of Edward II, was crowned at age 14 after his father was deposed by his mother and her consort Roger Mortimer. At age 17, he led a successful coup against Mortimer, the de facto ruler of the country, and began his personal reign. Edward III reigned 1327–1377, restored royal authority and went on to transform England into the most efficient military power in Europe. His reign saw vital developments in legislature and government—in particular the evolution of the English parliament—as well as the ravages of the Black Death. After defeating, but not subjugating, the Kingdom of Scotland, he declared himself rightful heir to the French throne in 1338, but his claim was denied due to the Salic law. This started what would become known as the Hundred Years' War.