Bishop Cuthbert Tunstal of Durham (1530-59), civil servant, scholar, and friend of Erasmus and Sir Thomas More, may also claim distinction for his building activity at Durham Castle. During his episcopacy he constructed the gallery fronting the twelfth-century work of Bishop Puiset, the lower stages of the clock-tower, and the chapel since generally known by his name. This last work superseded the original Norman chapel which must, by the second quarter of the sixteenth century, have become increasingly unsuitable for the everyday use of the bishop's household. The Tunstal chapel (plan, fig. 1) was enlarged by Bishop Lord Crewe (1674–1721), who added two more bays to the east, the termination of Bishop Tunstal's work being at a point corresponding to the west jamb of the second window from the east. The chapel is situated on an upper story, the room below now being the University College Junior Common Room. The builders made use of the foundations of a shorter earlier building, the east wall of which (plan, fig. 1, section BB) was retained as a limit to the lower room and as a support for the chapel floor. Nevertheless, beyond this wall the east bay of the chapel overhung the sloping side of the motte, leaving a triangular space beneath the floor (section AA, fig. 2). They therefore packed this space with large stones and rubbish, which included broken pottery, the whole being sealed by a layer of rubble and mortar on which the chapel floor could be laid. Just below the rubble a drain formed by a U-shaped piece of lead with a stone cover ran to a weep-hole in the south wall.