The very fact that Bulleid was even able to build any new locomotives at all during WWII is, in my opinion, a testament to determination and dogged persistence. Even a "legend" such as Gresley on the L.N.E.R. (where Bulleid had worked as Gresley's assistant) had to resort to pairing used tenders with his new build V2 Class, which arguably has a claim to be one of the locomotive types acclaimed as "the engine which won the war". The Men at the Ministry were contending with a steel shortage, caused at both ends of the production process (At the input side - loss of iron ore imports and shortages of wagons, locomotives and rail capacity to carry substitute domestic ironstone production due to disruption of coastal shipping. At the output end, multiple demands by military and civilian customers). I can see many difficult meetings where the Ministries would have preferred any other option over that of approving Bulleid's request to actually consume new materials. James Holland's new book on the Normandy campaign mentions early on about the role of logistics and shipping availibility was right up there as a pinch point in getting men, equipment and materials across the channel. Of course railway transport was the feeder to that shipping but not quite enough academic research has gone in to the sheer amount of juggling of priorities in balancing out the different cogs in the conveyor belt, let alone the even bigger picture of deciding just who went where in the queue for production. "Bomber Harris" would quite happily have had every ton of metal the UK could turn out to be used on building bombers. With hindsight (oh that "Monday morning quarterbacking" as the Americans call it) it is argued that if Churchill or even Portal had forced Harris to divert Liberator bombers to RAF Coastal Command the Battle of the Atlantic could have been won as much as a year earlier than it was (which would have possibly increased the supply of materials over that year). Now see where Bulleid would have been in that political furnace to get forty locomotives built. Everything that could be dispensed with in operating a locomotive had to be ditched. I would not be surprised if the provision of a cab was only approved to reduce firebox glare in the blackout rather than any concern over protection for the footplate crew.