The two side-aisles continue round the semi-circular apse, forming an ambulatory surrounded by five shallow radial chapels. The central chapel is consecrated, as usual, to the Virgin. The pointed vaults of the chapels unite with those of the ambulatory, eight pointed ribs meeting in the same key-stone.
The choir, scarcely touched by enemy fire up to December 1916, suffered more serious damage then and in January 1917.
Shells pierced the vault in two places and also penetrated several parts of the triforium wall, breaking the arches. In the apse, portions of the vault were injured and parts of the 13th century stained-glass, which it was not possible to remove from the high windows, were damaged.
The vital parts of the choir escaped serious damage, and it was possible during the second half of 1917, to carry out temporary repairs after the retreat of the Germans. At the same time, in order to make the choir—as well as the transept, which had also escaped serious injury—once more available for public worship, a partition was built shutting off the nave (photo p. [24]).
This protective partition shielded part of the building very effectively in 1918, when the Choir and Transept escaped serious damage.
Most of the fine 13th century stained-glass windows were removed in 1915 to a place of safety.
They were originally taken from the church of Saint-Yved-de-Braines and inserted during the 19th century in the high windows of the apse and those of the Lady Chapel.
Thanks to the protective measures taken, the interior decoration of the choir escaped injury. It dates from the 18th century and comprises a high altar of marble, surrounded by a wrought-iron railing, and flanked by two marble statues of the Virgin and the Angel Gabriel, depicting the Annunciation. Two consoles of carved and gilded wood with marble tops, complete this group. The stalls only are 17th century.
The North Arm of the Transept.
The north arm of the transept, flanked by aisles, shows the same arrangement as the nave, but ends in a straight wall (late 13th century) which was ornamented in the 14th century. A clerestory gallery joining the triforium of the side walls, and carried on small, light columns, is built against this wall. Above are pierced a row of bays and a fine rose-window containing old stained-glass.