The years circa 1155-72 must have been a period of feverish activity in the town, not only was the Castle under construction, but at the same time the Church was being built, two major projects at the same time. The ruined arches of the old Norman choir are still standing at the east end of the church. Wilmar the Chaplain became the first rector of the parish and a list of all subsequent rectors is on display in the church.
Inside the church there is an impressive screen stretching from North to South with Christ crucified and flanked by His mother and St John above it. Along the upper part is intricate wood carving. The screen was erected in memory of the Revd Edward Maude Scot who was rector from 1877-1901 and died in 1917.
Behind the screen are stalls for the Clergy and choir and behind them a paneled screen dated 1712 in which is set the Royal Arms of King William 3rd. There is part of the old Organ Gallery dated 1772 which was most uncommon at that time. The present organ was bought secondhand in 1903.
The 15th century font has a Latin inscription round the base which translated reads "Pray for the souls of John Cokerill and his wife Catherine who caused this font to be erected in Gods honour.
There are many other items of interest in the church including a comparatively recent addition which is a circular slate plaque set in the floor near the entrance to the belfry commemorating the premieres of three of Benjamin Brittens works which were performed here.