On 11 February 1225, King Henry III (r. 1216–72) issued what became the final and definitive version of Magna Carta. It is clauses of the 1225 charter, not the charter of 1215, which are on the Statute Book of the United Kingdom today. The 1225 Magna Carta, in terms of its content, had far more status and authority than the versions issued in 1216 and 1217, during Henry’s minority. The 1225 version of Magna Carta was authenticated with the Great Seal of Henry III himself, which had been introduced in 1218, and it also removed, once and for all, any suggestion that its liberties were the product of coercion. In its final clause Henry declared that, in return for the charter, everyone in the kingdom had given him a tax amounting to a 15th part of their moveable property. The charter was thus part of a bargain freely entered into between king and kingdom.

Reflecting this new consensus, the 1225 Magna Carta, in contrast to its predecessors, had a long list of witnesses. Headed by Archbishop Stephen Langton (1150–1228), there followed the names of 11 bishops, 20 abbots, nine earls and 24 other magnates and ministers. Langton and the bishops also supported Magna Carta, as they had not done before, by promulgating sentences of excommunication against all who contravened it.

The 1225 charter was circulated to the counties and given great publicity. Four originals survive, with this one having a note on the back, reading ‘by deposit of the knights of Wiltshire’. This presumably refers to the way the knights of that county had placed their copy of Magna Carta for safekeeping in Lacock Abbey. This copy of Magna Carta was preserved at Lacock until it was presented to the British Museum in 1945, before finally entering the collections of the British Library.