Apparently, at the close of the First World War of the British officers demobilised something like 40% of them were judged to be working or lower middle class. I wonder if in our supposedly more meritocratic age whether the present officer corps shows the same level of job opportunity. I doubt if it even comes close. In 1918 there was a war on. There was a real job to do and not getting it done could have proved very costly. So, merit rather than parental wealth became an a very important criteria. But the British Army breathed a sigh of relief in  1918 and got back to "proper soldiering". It believed it had nothing at all to learn from the conflict. It therefore took until late 1942, and many would argue even later, before the army was fit for purpose. The Germans on the other hand not only learned from their experience during the First World War but from the victorious British Empire forces. The result was a very close run thing in 1940.