Iain W said -

at the time the series was written/broadcast, the threat of nuclear war was a real possibilty

Maybe other list members who were in their "formative years" in the 1970's would like

to

comment on my perceptions

I would agree with you that people were generally scared of nuclear war in those day. It was almost a reflex cliche, when talking about the future, for example on TV or in the pub, people would prefix their comments with 'assuming we haven't all blown ourselves up by then' or something along those lines. I don't hear people use that expression as commonly these days. They talk about global warming and super-viruses and so-on instead.

Alison