Kirby Muxloe Castle, four miles west of Leicester, is the companion of Ashby Castle, being the work of William, Lord Hastings. Although a license to crenellate was granted in 1474, construction did not commence until October 1480, by which time Ashby was nearing completion. The building accounts, which survive in full, give a total expenditure of 1088 pounds on the incomplete castle.
An older manor house occupied the site and some of its foundations are visible in the courtyard. Unlike Ashby, where Lord Hastings utilized existing buildings, Kirby Muxloe was completely rebuilt on quadrangular lines. It is oblong rather than square in plan. Kirby also differs from Ashby in the choice of brick as the main building material, stone being used only for doorways and windows.
The low revetment wall, which defines the courtyard, rising out of a water-filled moat, marks the position of the intended curtain and its square angle towers. Only two portions, the gatehouse and the west corner tower now stand, though more must have been built.
The gatehouse is a ruin and is known to have been left incomplete. It is a sturdy, oblong structure with semi-octagonal flanking towers and stair turrets at the rear. The angle tower has fared better because it is still intact, including the battlements, though now a shell.
Kirby Muxlor was one of the last castles built with some serious regard for defense. A drawbridge, a portcullis and two pairs of gates defended its gate passage, and gun ports pierce both the gatehouse and the surviving tower. These gun ports, however, are the primitive type, which are pierced by gun ports. These gun ports, however, are the primitive type that had been in use for over a century – small roundels permitting only a limited range of fire.