Small parts of St Martins Cathedral date back to the 12th century, but it was much altered and restored in the 19th C. and little of the old fabric remains. It was a parish church, then Collegiate church from 1922, and in 1927 it became a Cathedral. There is a nave, chancel, chancel chapels, north and “double” south aisle, crossing tower with 220 foot spire, and north and south porches.

The north and south arcades of 5 bays date from the 13th century, with the outer south arcade built slightly later. There is a 13th century north doorway and porch, but the main entrance is through the south door with porch by G. F. Bodley of 1897.

The tower and spire were rebuilt in the mid 19th century in an Early English style, replacing the mediaeval spire. There were many restorations covering almost the whole of the church in the 19th century.

There are numerous monuments and wall plaques in the Cathedral.

In March 2015 the remains of King Richard III were reinterred at the Cathedral beneath a new tomb installed in the chancel.

The east window is by Christopher Whall, there are also windows by Veronica Whall, and there is a new pair of windows in the north chancel chapel (Saint Katherine's chapel) by Tom Denny, which were installed in 2016.