I haven't listened to radio 4 in a long time, so can't comment on its "decline", if there is one. But why the embarrassment? You're a grown woman with life experience and, I imagine, your GS wasn't unfamiliar with the subjects either. So what's there to be embarrassed about? I discuss all sorts of subjects with my GC, nothing is off the table (with their mother's permission, of course). Their mother, my DD, has made it hers life work to try and embarrass me, by talking about absolutely "everything". She's yet to succeed, but she keeps trying... 
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