The floor above had to be reinforced before a new ceiling was put in, as the plaster would continue to crack unless properly addressed.
Two steel beams were installed within and below the ceiling joists. The beam spanning left to right is a T-beam and sits inside the joists via slots cut within them. It is then bolted via a welded plate to a single large box section of steel running perpendicular to the T-beam. All the steel rests upon brick within the interior walls and slate padstone shims on the exterior wall: