The commercial success of the port, which rapidly became the most important on the south coast, brought in lots of money in the form of harbour dues and the inhabitants soon became even more ambitious. First the nave was enlarged in about 1130 by adding aisles. Then in the 1170s the chancel was completely rebuilt on a cathedral scale.
It is a text-book example of a cathedral choir of the Transitional style, when Norman was morphing into Early English, with an arcade of large arches at the bottom, a triforium (a line of arches looking out into the roof of the aisle) and a clerestory (a line of windows under the roof arches) and a stone vaulted ceiling.
The details of the choir are conflicting and have been the subject of furious debate among historians, some seeing the influence of the great William of Sens, builder of Canterbury Cathedral, others of masons based in Chichester and Boxgrove.
The finished church must have been truly magnificent, but sadly New Shoreham went into a decline in the 15th century when the harbour silted up.
The choir was the responsibility of the rector and was maintained, but repairs to the nave, which should have been paid for by the now cash-strapped ratepayers, was neglected. Damage may have been sustained in a French raid in 1628, then in the Civil War and finally in the Great Storm of 1703. Eventually the tottering structure was demolished and some of the stone used to create a west porch against the tower.
In the 19th century New Shoreham's fortunes revived as new docks were constructed extending to Portslade, and several schemes were hatched to rebuild the nave. Perhaps fortunately none came to fruition and today, like Boxgrove Priory, the church stands proudly but a little lopsidedly with its great choir to one side of the tower and a few piles of stones on the other.