The south transept was built in the 14th century, the north transept in the early years of the 15th century. The great tower was complete by 1450. The chapel replaced the parish church of St. John and continued to serve as the parish church as well as the chapel until 1891. Because of this, it is generally referred to as Merton Church in older documents, and there is a north door into the street as well as doors into the college. This dual role also probably explains the enormous scale of the chapel, which in its original design was to have a nave and two aisles extending to the west.See Bott, pp.24–37
