exists in Winchester, Salisbury, Durham, Albans, Exeter, Ely, Wells and Peterborough Cathedral, except that in those cases (except Wells) the eastern chapels are square; in Wells Cathedral the most eastern chapel (the Lady Chapel) has a polygonal termination; in Durham Cathedral, the chapels are all in one line, constituting the chapel of the altars, which was probably borrowed from the eastern end of Fountains Abbey. In some of the above designs, original design has been transformed in rebuilding; thus in Albans, Durham, York and Exeter cathedrals, there was no ambulatory but three parallel apses, in some cases rectangular externally. In Southwell, Rochester and Ely, there was no processional path or ambulatory round the end; in Carlisle no eastern chapels; and in Oxford only one central apse. Chevets The earliest example of the chevet is probably to be found in the church of St Martin at Tours; this was followed by others at Tournus, Clermont-Ferrand, Auxerre, Chartres, Le Mans and other churches built during the great church-building period of the 11th century. In some cases they used the old foundations, as in Chartres, Coutances and Auxerre cathedrals. In others, such as at Le Mans, they extended the eastern termination, much in the same way as in many of the early examples in England, except with this important difference: when the apsidal east end was given up in the middle of the 12th century in favour of the square east end in England, the French developed it by doubling the choir aisles and adding to the number of extra chapels. This is demonstrated by the number of apsidal chapels in various churches: Three: Canterbury, Norwich, and Gloucester; Five: Noyon (1150), Soissons (1190), Reims (1212), Tours, Seez, Bayeux (1230), Clermont (1275), Senlis, Limoges, Albi and Narbonne; Seven: Amiens, Le Mans and Beauvais; Nine: Chartres. Double aisles round the choir, of which there are no examples in England, are found in the cathedrals of Paris, Bourges and Le Mans. The cathedral of Sens (1144–1168) possesses one feature which is almost unique: the coupled columns of the alternate bays of nave and choir and of the apse. These were introduced into the chapel of the Trinity in Canterbury cathedral, probably from the designs of William of Sens, by his successor William the Englishman. The square east end found no favour in France, with Laon, Poitiers, and Dol being the only cathedral examples. Of the triapsal