"he considers that enough to equip him with the necessary skills to be SoSDef then holy moly. And he knows deeply about defence because his forebearers fought in WW2."
To be fair it is not a requirement of the UK Cabinet system for a Minister to have ANY experience or knowledge of the Ministry she/he heads. In fact if you do have that knowledge you're seen as a possible insider with already fixed views. Health Ministers are rarely Doctors, Education Ministers almost never teachers