West side of upper north transept seen from the chapel roofs

Having become accustomed to the forms of the clerestory and flying buttresses of the nave the perceptive visitor will notice a number of changes in the upper west transept. Here you can see that the middle bay of the transept clerestory (to the right) now has groups of three lancets topped by trefoils: the tracery pattern in the nave had embodied paired lancets topped by circular oculi. We are seeing the different approaches to design on the part of a father and a son: Thomas of Cormont in the nave and Renaud in the upper transept. Note: the outermost bay of the transept, narrower, has paired lancets topped by trefoils.