The tower, joined to the south range of college buildings, is built in four storeys unequal in height. Octagonal turrets encase the corners; the slightly larger northwest turret encloses the spiral stair, lit by slit windows. The basement is windowless; the second and third stages have small windows in three sides; the fourth, principal storey is loftier, with a double window on each face divided by a buttress rising through the panelled frieze and mock battlements, where it is surmounted by a figure in a niche crowned by a pinnacle slightly smaller than the four pinnacles that crown the corners.