The three narrow 12th-century lancets to north and south have wide splays on the interior in order to maximise the amount of light. Traces of 12th-century(?) painting recorded on the splay of one of the north windows have subsequently been painted over. It is likely that the east wall had three lancets, broadly similar to the present three inserted in 1871 to replace a flowing traceried window that had been inserted in the late 14th century as part of a major refurbishment of the chancel. Beneath that window was an inscription: ‘Orate pro anima fratris Alexandri de Bury qui istam fenestram fecit‘ [Pray for the soul of brother Alexander of Bury who commissioned this window]’. Alexander may have been the Guest Master at Ely in the late 1370s. In 1190 the bishop had allocated £10 of the tithes from Meldreth to support the Guest House of the priory.
A vestry was built out onto the north side, the (blocked) opening to which is clearly visible on both sides of the wall. This was demolished just before 1685, when it was referred to as ‘lately pulled down’.
A two-light window, with flowing tracery, was inserted into the northwest corner of the chancel; its horizontal transom would have allowed opening shutters in the lower part of the window. This window may have been required as the construction of the vestry would have blocked the two 12th-century windows. Fragments of medieval stained glass have been reset in this window showing St John the Baptist (15th century, head probably a later restoration) and a kneeling monk (probably 14th century, perhaps the donor from the east window). The chancel was also provided with a piscina (for washing the sacred vessels), unusually on the north side, and two aumbries in the east wall (in which to keep the vessels for the Mass, the chalice and paten etc). Probably at this time, though possibly in the 15th century, the chancel was also decorated with wall paintings, fragments of which remain, though in poor condition. On the north wall St Margaret of Antioch? and St Christopher, and on the south wall traces of a figure in a red chasuble. The traces of blue and gold around the piscina reported by Palmer are no longer visible.