Due to the treaty of Norham, 7 August 1209,[3] King William was forced to submit to a peace and send Isabella and Margaret to England as hostages.
[2] The sisters were imprisoned at Corfe Castle along with Eleanor, the Fair Maid of Brittany,[1] who had been under house arrest to prevent her claim on England.
[citation needed] Isabella and Margaret were both intended in marriage to John's sons[4] and the Scots made a payment of 15,000 marks,[5] equivalent in modern values to tens of millions of pounds, to pay for these royal weddings.
[3] The ladies were sometimes allowed to ride out under the strictest guard and were treated in good form as befitted their rank, but Isabella and Margaret's potential marriages continued to be delayed by John throughout the 1210s and early 1220s, demonstrating of his power over Scotland.
King Alexander demanded that his sisters be married as had been agreed,[4] with the concessions that they were only required to be found 'suitable' husbands and not the royal princes that were originally promised.
King John's son and successor Henry III of England granted Isabella property when she married Roger in May 1225.