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Further desertions of John's local allies at the beginning of 1203 steadily reduced John's freedom to manoeuvre in the region. He attempted to convince Pope Innocent III to intervene in the conflict, but Innocent's efforts were unsuccessful. As the situation became worse for John, he appears to have decided to have Arthur killed, with the aim of removing his potential rival and of undermining the rebel movement in Brittany. Arthur had initially been imprisoned at Falaise and was then moved to Rouen. After this, Arthur's fate remains uncertain, but modern historians believe he was murdered by John. The annals of Margam Abbey suggest that "John had captured Arthur and kept him alive in prison for some time in the castle of Rouen ... when John was drunk he slew Arthur with his own hand and tying a heavy stone to the body cast it into the Seine."[nb 7] Rumours of the manner of Arthur's death further reduced support for John across the region. Arthur's sister, Eleanor, who had also been captured at Mirebeau, was kept imprisoned by John for many years, albeit in relatively good conditions.

Who was kept imprisoned by John for many years?
Eleanor