16th November
1272 – While travelling during the 
Ninth Crusade, 
Prince Edward becomes King of England upon 
Henry III of England's death, but he will not return to England for nearly two years to assume the throne. This was due partly to his still-poor health, but also to a lack of urgency.The political situation in England was stable after the mid-century upheavals, and Edward was proclaimed king after his father's death, rather than at his own coronation, as had until then been customary.
Edward I also known as 
Longshanks and the 
Hammer of the Scots, was 
King of England from 1272 to 1307. Concurrently, he was 
Lord of Ireland, and from 1254 to 1306, he ruled 
Gascony as 
Duke of Aquitaine in his capacity as a 
vassal of the 
French king. He held his 
coronation on 19 August at Westminster Abbey, alongside Queen Eleanor. Immediately after being 
anointed and crowned by 
Robert Kilwardby, the 
Archbishop of Canterbury, Edward removed his crown, saying that he did not intend to wear it again until he had recovered all the crown lands that his father had surrendered during his reign.
He set about the conquest of Wales;  Llywelyn ap Gruffudd enjoyed an advantageous situation in the aftermath of the Barons' War. The 1267 
Treaty of Montgomery recognised his ownership of land he had conquered in the 
Four Cantrefs of Perfeddwlad and his title of 
Prince of Wales. Llywelyn's younger brother 
Dafydd and 
Gruffydd ap Gwenwynwyn of 
Powys, after failing in an assassination attempt against Llywelyn, defected to the English in 1274. Citing ongoing hostilities and Edward's harbouring of his enemies, Llywelyn refused to do homage to the King. For Edward, a further provocation came from Llywelyn's planned marriage to 
Eleanor, daughter of Simon de Montfort the Elder.
In November 1276, Edward declared war and in July 1277 Edward invaded with a force of 15,500, of whom 9,000 were Welshmen. The campaign never came to a major battle, and Llywelyn soon realised he had no choice but to surrender. By the 
Treaty of Aberconwy in November 1277, he was left only with the land of 
Gwynedd, though he was allowed to retain the title of Prince of Wales.
When war broke out again in 1282, it was an entirely different undertaking. For the Welsh, this war was over national identity, enjoying wide support, provoked particularly by attempts to impose 
English law on Welsh subjects. For Edward, it became a war of conquest rather than simply a 
punitive expedition, like the former campaign. The war started with a rebellion by Dafydd, who was discontented with the reward he had received from Edward in 1277. Llywelyn and other Welsh chieftains soon joined in, and initially the Welsh experienced military success. On 6 November, while 
John Peckham, Archbishop of Canterbury, was conducting peace negotiations, Edward's commander of 
Anglesey, 
Luke de Tany, decided to carry out a surprise attack. A 
pontoon bridge had been built to the mainland, but shortly after Tany and his men crossed over, they were ambushed by the Welsh and suffered heavy losses at the 
Battle of Moel-y-don. The Welsh advances ended on 11 December, when Llywelyn was lured into a trap and killed at the 
Battle of Orewin Bridge. The conquest of Gwynedd was complete with the capture in June 1283 of Dafydd, who was taken to 
Shrewsbury and executed as a traitor the following autumn; Edward ordered Dafydd's head to be publicly exhibited on 
London Bridge.
Increasingly after 1283, Edward embarked on a project of English settlement of Wales, creating new towns like 
Flint, 
Aberystwyth and 
Rhuddlan. Their new residents were English migrants, the local Welsh being banned from living inside them, and many were protected by extensive walls. An extensive project of castle-building was also initiated, under the direction of 
James of Saint George, a prestigious architect whom Edward had met in Savoy on his return from the crusade. These included the 
Beaumaris, 
Caernarfon, 
Conwy and 
Harlech castles, intended to act both as fortresses and royal palaces for the King.
By the 1284 
Statute of Rhuddlan, the 
principality of Wales was incorporated into England and was given an administrative system like the English, with counties policed by sheriffs. English law was introduced in criminal cases, though the Welsh were allowed to maintain their own customary laws in some cases of property disputes. Later in 1284, King Edward had his son Edward (later 
Edward II) born at Caernarfon Castle, probably to make a deliberate statement about the new political order in Wales.  In 1301 at Lincoln, the young Edward became the first English prince to be invested with the title of Prince of Wales, when the King granted him the Earldom of Chester and lands across North Wales.