The outside gives some of this away, with a variety of roofs over different parts of the building, and a large and grand more or less detached bell tower. This was the last significant part of the church to be built, in the 1530s, after the previous tower had collapsed in a storm nearly a century earlier.
The interior is most unusual in that it has two naves and two chancels. This came about because in medieval times the mouth of the River Ouse was just to the east of the church (before the Ouse was completely re routed), while immediately to the west was the castle moat and mound. So when an expanding population required a bigger church, the often adopted solution of making a longer nave was not an option, and the church was made wider instead.
Features of the different ages and phases of this building and rebuilding can most clearly be seen in the piers and arcades of the two naves. Some are from the original Norman church, while others are from the 13th and 15th centuries. The work was not at all straightforward, which can be seen at the northeast end, where the medieval masons were obliged to 'bodge' the join between chancel and nave. When the old tower blew down in the 1400s it fell into the body of the church, making further rebuilding necessary. At this point the two naves were given a shared roof, supported by a central arcade of columns. This makes it one of only two such arrangements in England.