Two years on, I can exclusively reveal that, not for the first time, my memory wasn't serving me well. I have indeed unearthed more radiogram shots and unexpectedly these include three taken after 1976. (Just yesterday evening, at the end of an undeveloped strip of negatives, I found one from the dreaded moustache period.) It now appears that the very last Radiogram photo was actually taken in 1981, on my 21st birthday. There are still gaps to be plugged though, so there may well be further updates to come, somewhere down the line.
Meanwhile, here I am 50 years ago today, wearing a fetching bow tie & shorts combo and looking as if butter wouldn't melt in my mouth. I got a good haul for my 4th birthday, including a basketball, my first big-boy's bike (stabilisers hidden behind the jigsaw puzzle) and, crucially, a transistor radio. My very own personal source of music. Life would never be quite the same again.
(Great song, sorry about the shocking clip!)