Archæologists have traced the handiwork of three different men in Le Mans' choir. First, an architect of the Ile-de-France made the general plan, and built the thirteen radiating chapels. Then a Norman worked on the eastern curve, and it is thought he was Thomas Toustain, cited here as master-of-works, since Toustain is a Norman name. Perhaps he was the same genius who had already planned the high inner aisle at Coutances Cathedral. Very Norman are Le Mans' circular capitals, the sanctuary's twin-column piers, the carved band under the clearstory, the sharp-pointed arches beneath arches, and the foliate sculpture covering the spandrels of the aisle's triforium. The third master-of-works must have been a native of the Ile-de-France, for the upper choir and the two bays nearest the transept belong to that school.
There is a progressive enlarging of the bays of the choir from its entrance to its end, done too regularly to have been accidental. Professor Goodyear has developed the thesis of these intentional refinements in Gothic monuments.[166] Mr. Arthur Kingsley Porter thinks that undoubtedly there are cases when it was done with subtle design, but more often the irregularities resulted from the sound artistic taste of the old masters who preferred a free-hand drawing to mechanical perfection. "There is no excellent beauty that hath not some strangeness in the proportion," said Bacon. Some think that at Le Mans the desire was to counteract the perspective narrowing. Others say that the builder thought thus to conform the wide choir to the ancient nave of lesser breadth.
Not till the day of Rayonnant Gothic was Le Mans' transept begun, and it proved exceptional in continuing building while the foreign wars ravaged France; the chapter taxed itself heavily to meet expenses. As the XIV century closed, the southern arm was finished; it is entirely blocked by the ancient tower, to which were then added two stories. Midway in the vertical wall of the northern arm (begun in 1403) appears Flamboyant tracery. As cracks soon showed, the chapter called in a new architect, Jean de Dammartin, whose grandfather and great-uncle had beautified Dijon, Bourges, and Poitiers. When in 1430 the English captured Le Mans, he passed to Tours, on whose west façade he worked.