The building was subject to assessment in 2000 (SUP 9) and a programme of historic building in 2011, prior to demolition; the south-east end had been demolished by the MOD prior to recording.

MCC3123 was essentially identical to MCC3122, to the south, at the time of construction. The only differences occur in the later alterations. Here the entrances on both of the long elevations have been widened to accommodate double wooden doors, with those on the north-eastern side subsequently bricked in, presumably when Circular Road West was constructed. The entrances to the main stable block on the north-west elevation have also been altered, again with one being subsequently bricked in. The storage shed on this elevation retains the original door and window but has had a later Crittall metal-framed window inserted into its long side. The north-west and north-east elevations have also been painted off-white. There are surviving tethering rings in the same locations as in MCC3122, and a hay-bag tie can be observed on the south-west elevation near to the storage shed.

The interior of the building is a large empty space subdivided into three unequal parts. Two of these divisions are formed by wooden stud walls, the third by a concrete block wall with a door located off-centre. The building had been demolished up to this wall at the time of recording. The floor is of concrete, and wooden trusses held in place with iron bolts and strapping support the roof. The original internal plan would have been the same as MCC3122 and there would have been identical litter sheds and water troughs attached to the long sides. <1>