 The inside cylinder was to be actuated by Holcroft's design of conjugated valve gear, which consisted of mechanical links fitted to both sets of outside Walschaerts gear, eliminating the need for a separate set of valve gear between the frames to operate the inside cylinder.The result would be a reduction in weight and the amount of mechanical equipment in this inaccessible part of the locomotive.Holcroft’s valve gear design was also an attempt to address the problems associated with Gresley’s conjugated valve gear, which was prone to variations in valve events caused by heat expansion of the valve spindles within the pistons.