Though some of the pre-grouping railways had issued diagram books for wagons of special construction for the carriage of large, heavy or out-of-gauge loads others don’t appear issued anything beyond a general diagram book covering principal wagon types. The North Eastern and North British Railways are two notable examples.
In order to utilise its entire stock of specially constructed wagons inherited from the pre-grouping companies the newly created LNER Central Wagon Control office, located at York, compiled and issued a consolidated list and diagram book covering all special wagon types extant in 1926. Spare pages ready to receive amendments were included. Although the new LNER book did not include allocation details otherwise it was in a fairly similar style to the previous NER books complete with route restrictions. As new LNER wagons types were designed and introduced to traffic following the issue of the book in 1926 an amendment slip was circulated containing a diagram and wagon numbers – the receiver of the amendment was supposed to paste it into the book.
Wagons were grouped by type (implement, machinery, flat, etc), generally following NER practice with a few minor amendments. Each type receiving a code (IMP, MAC, FLAT, etc) and a letter suffix (A, B, C, D, etc) for each different wagon design within that type.