The westernmost bay of the nave has been formed into a kind of vestibule by means of the archways constructed, during the last century, to strengthen the towers at that end. The vestibule is in three compartments, two of which, under the western towers, are square. The centre one is the most interesting, since it preserves to us a portion of the first bay of Remigius' nave. High up in the side walls is a Norman arch, part of the original clerestory. Below this we can trace the outline of a wider arch (now filled in), which belonged to the triforium. Considerable alterations were made in these walls by Treasurer Welburne in the second half of the fourteenth century, and the arches were filled in during the early part of the eighteenth century, owing to the instability of the towers. The arch dividing the vestibule from the nave was constructed by an architect named John James (apparently not James Gibbs, as some have supposed) about the year 1730, and altered by James Essex thirty or forty years later. In the time of Bishop Grosseteste (1235-53) the side walls were carried above the Norman clerestory to the height of the present nave, and covered with the characteristic lattice-ornament which we have already seen in the central arch outside. The great west window was also inserted in Grosseteste's time, as well as the cinquefoil window above. The tracery now filling the former is in the Early Perpendicular style, and dates from the end of the fourteenth century. From the broad sill of this window a good view of the interior can be obtained, and a much finer one still from the passage which runs beneath the other window above. From the latter position we have an uninterrupted view of the entire length of the minster, which looks longer than it really is, from the fact that the vaulting is carried at an almost uniform height throughout.
In the floor are slabs bearing the names of Chancellor Reynolds (d. 1766) and of Precentor Trimnell (d. 1756), the "chanter" who was accused of removing the statues over the central doorway outside. On the wall at the north-east corner is a tablet to the memory of the officers, non-commissioned officers, and privates of the 10th or North Lincolnshire regiment of infantry, who died in the campaigns of the Sutlej (1845-46) and of the Panjab (1848-49); the tablet was erected by their surviving comrades. The compartments under the western towers were vaulted by Treasurer Welburne (ab. 1350-80), to whom is also due the tracery which covers the walls. The curious chambers constructed in the thickness of the old Norman west front are accessible from the sills of the western windows, these being joined by narrow passages in the wall. On the north side we are able in the same way to reach a long narrow chamber, which probably served as a treasury, constructed in the north wall of the tower. The chamber was originally lighted by four small round-headed windows. One of them, on the west side, is still open; the two facing northwards, formerly outside windows, are now enclosed by the northwest chapel, and blocked up; the fourth, on the east, is also blocked. A square hole in the floor formed at one time the only means of access to the chamber beneath, which may now be reached by a doorway from the porch. In the north wall of this lower chamber is a low semi-circular arch, supposed to have been constructed by the Norman builders, in order to avoid some obstacle in the way of the foundations. This arch was filled in with masonry, now pierced by a doorway. The north-west chapel, which is entered by this doorway, encloses the outer wall of St. Mary's tower.
The corresponding chapel on the south side of the minster is sometimes called the "Ringers' Chapel." On its walls is painted a seventeenth century list of the "Names of the Companie of Ringers of our Blessed Virgen Marie of Lincolne." In one place we see "Edward Whipp 1617 at the kings coming to Lincolne." This refers to the visit of King James I. in March of that year, when he visited the minster, and touched a number of persons for the evil. His Majesty went also to a cock-fight at an inn near the Stone-bow, and to a horse-race on the Heath. Edward Whipp was evidently one of those who rang the bells in honour of the royal visit. The Ringers' Chapel encloses part of the south wall of St. Hugh's tower, which has a large arched recess and a niche, similar to those in the west front.
The curious "stone beam," about which so much has been conjectured, and so little is known, is constructed between the walls of the two western towers, just above the stone vault of the nave. It is really an arch of very slight curvature, composed of twenty-three stones of unequal length, but of uniform depth and breadth. Examination has proved that there is nothing but mortar in the joints, and there are no traces of iron having been used in the construction. When jumped upon, the "beam" vibrates appreciably. It has been suggested that it was constructed in order to try whether the towers were capable of supporting the additional weight of upper storeys, but nothing appears to be satisfactorily known as to the purpose it served or the date of its erection.
The Nave was constructed, together with the two chapels at its western end, during the first half of the thirteenth century. Attempts have been made to distinguish earlier and later features in different parts. For example, the morning chapel on the north side is considered to be somewhat earlier than the consistory court opposite to it; but there being no documentary evidence to guide us, all that we may safely say is, that the nave is later than the time of St. Hugh (d. 1200), and was practically completed before the death of Bishop Grosseteste, which occurred in 1253. Taken as a whole, it is one of the best examples of the Early English style we possess. The late Sir G. G. Scott, in his lectures on Mediæval Architecture, thus speaks of it—"It exhibits an Early English style in its highest stage of development: massive without heaviness, rich in detail without exuberance, its parts symmetrically proportioned and carefully studied throughout, the foliated carving bold and effective, there seems no deficiency in any way to deteriorate from its merits." In dignity especially, the eminent architect considered the nave to be superior to all other parts of the cathedral.