The stream was altered greatly in Saxon and early Norman times. There was a mill here even before the castle existed. In the winter of 1142, there was a siege at the castle.[5]Empress Matilda (aka Queen Maud, 1102–1167), the daughter and dispossessed heir of Henry I, was there during her power struggle with King Stephen (1096–1154). The queen escaped from the castle after her guards lowered her over the walls. She was clothed in a white dress that camouflaged her against the snow. Matilda crept through the enemy lines and across the Castle Mill Stream to escape to freedom.
In the Middle Ages, the stream was used for navigation, at least above Hythe Bridge. During the 16th century, hay, wood, stone, and slate were unloaded at a wharf at Hythe Bridge.[6] When the Oxford Canal was built, it provided an easier route into the centre of Oxford, and in 1795-96 Daniel Harris built Isis Lock to allow Thames river traffic to access the canal wharves. The stream then fell out of use for navigation.