They are not just at the corners, but in the middle of the sides as well; the west one has obliterated the west door. The buttresses are of various dates, some perhaps original, but one at least is from 1598 (it is dated), and further reinforcing work was carried out in the 1970s. The tower itself dates from the late 13th century.
The nave clerestory appears to be built of yellow brick, but this is only a refacing done in the 19th century.
The church houses a magnificent screen, all the more special because it still has its loft, complete with ribbed coving.
In the chancel is a complete set of 14th century stalls. Their main decorative motif is ogee headed arcades, but they also have carvings of a much less formal nature on the arm rests and on the misericords. These include birds, animals, mythical creatures and people.
On the chancel floor are two large brasses to former rectors of Holy Trinity: John Sleford, who died in 1401 and John Blodwell, who died in 1462. Both are magnificent, that to Sleford marginally more so. He was no mere Vicar, but also, among other things, Keeper of the Wardrobe to Edward III.