wwI

British heavy tanks were built in factories scattered across the country from Birmingham to Edinburgh and Glasgow. Each factory had its own testing grounds and was situated at or near to a railway. Most factories had their own sidings and a marshalling yard. After testing a new tank would be loaded onto a railway wagon. This represented the first problem, as there were no wagons suited to carrying heavy tanks. Those bogie–bolsters that were used were at the limit of their carrying capability and it was not unknown for structural failures to occur. If this happened during transit the whole train would be delayed. Such wagons could only be loaded "end on" (photo above). This added a further source of delay as it meant that the wagons had to be loaded and then added to the train one at a time. This was solved by the design of the RECTANK wagon by a working party of tank officers and railwaymen under the aegis of the Landship Committee. These were strong enough and could be loaded from the side (photo below). Without the RECTANK the Mk V* could not have been transported. These wagons became available in adequate numbers in early 1918.
http://www.landships.info/landships/tank_articles/Tanks_to_the_Front.html