Donald Insall Associates was appointed to rectify water ingress threatening the ornate mediaeval stone carving in this Grade I listed Scheduled monument partially built between 1295-1298, then completed in 1306 with some elements left unfinished. Remedial works involved taking up the existing cobbled roof finish under archaeological supervision and providing a new membrane isolating new works from mediaeval fabric. Sandstone flagging with perimeter drainage channel was provided. New lead lined spitters dispersed water away from the historic fabric and channelled it off the main roof in to the outer ward below. The interior of the chapel was also re-floored using sandstone flags with discrete up-lighters installed to emphasise the intricate mediaeval carving. The walls were lime washed to encourage the fabric to dry out and discrete ventilation was introduced to the high level roof light.