of the choir was increased by making it occupy part of the space farther to the west.  Possibly it projected into the nave.  At the west end of each of the aisles of the nave a tower was placed, and between these two towers was the chief public entrance to the church.  From the subsequent history of the structure it would appear that the two western towers had been built up and finished, so far, at least, as was necessary to allow of the completion of the nave with its aisles and roofs.  The same may be concluded of the central tower.

This latter probably rose only just above the ridge of the roofs.  To carry it up so far would have been dictated to the builders by structural reasons; for such a height would be required to help the stability of the piers and arches below, since they had to resist a variety of opposed thrusts.  But even this tower, low as it no doubt was, like others of the same date, did not survive the dedication more than about twenty-six years.  The whole building was covered with a high-pitched wooden roof over the nave, transept, and chancel; and beneath the outer roof there was a flat inner ceiling of wood formed between the tie beams, similar to those now to be seen at Peterborough and S. Albans.  The north and south aisles of the nave were protected by roofs which sloped up from their eaves against the wall that rose above the nave arcades.  Internally the ceiling to these was a simple groined vault supported by transverse arches.

Immediately above the vault of the aisles was the gallery of the triforium.  This was lighted throughout by small external round-headed windows, some of which may still be seen embedded in the walls.  The aisles and ambulatory of the chancel were treated by the same methods.  In the triforium gallery, above the transverse arches of the aisles, were other semicircular arches.  These served a double purpose:  they acted as supports to the timber framework of the aisle roofs, and also as a means of buttressing the upper part of the nave walling in which the clerestory windows were placed.  Such other buttresses as there had been were broad and flat, with but little projection from the surface of the wall.  The windows throughout the building up to about the end of the twelfth century were small in comparison with some of those which were inserted at various times afterwards.

[Illustration:  View through the south triforium of the nave from the south-west tower. From a photograph by Mr. F. Bund.]

It has been remarked that the termination of the early chancel towards the east was an apse, and that round this was carried the north and south choir aisles in the form of a continuous ambulatory.  From this enclosing aisle—­a semi-circle itself in form—­three chapels were projected, each with a semicircular apsidal termination.  The central one of the three was the lady-chapel.  This consisted then of the three western bays only of the present chapel.  The lady-chapel was added about eighty years after the early part of the nave had been built, and has since been much altered.