I’m not quite sure of the timeline here. I know my dad did National Service after he was at Imperial College, and I think that included a Masters degree.
But, now that he’s been demobbed, it looks like he’s back at university. I think he said once that he started on a PhD but couldn’t finish it as the grant ran out. So, I’m guessing that this is the PhD period, especially as it looks like he started a proper job in 1959.