Shuttered sockets (with the shutters operated by the earth pin) have been the norm here in the UK since BS 1363 was initially introduced in 1947.
and not long after the safety dogooders without a clue started flogging plug in covers that managed to make a perfectly safe socket into something unsafe
I think the first time I saw the "safety" covers was in the 70s.
To be fair, in the 60s and 70s there were sockets on the market that weren't as good as they should have been, on which with a little determined poking you could push the shutters aside by poking at the shutter in front of the live or neutral with something pointy*. However, the standard was revised to require a positive interlock with the earth pin so now the shutters won't open without the earth pin in place whereas before frequently (but not always) all that held the shutters in place was a spring and they were merely pushed aside by the earth pin. I
think the requirement for a positive interlock was made in the same revision of BS1363 in 1984 as the introduction of insulated sleeving at the base of the live and neutral pins, but don't quote me on that.
*Back before fitting moulded plugs to all new appliances was law, it was common for things to come with bare wire ends on the mains lead and you were left to fit your own plug. More than once I saw some genius wrap the bare ends onto wooden matches, often leaving the ignitor compound in place, and push them into a wall socket after finagling the shutters open. The culprit was usually in the building trade, the appliance was usually a hand-held power tool of some sort, and the earth wire didn't qualify for the matchstick treatment because they needed the shutters to close to hold the matches in place and so had to have the earth pin position unoccupied.
Once upon a time, if I hadn't seen it for myself I'd have had difficulty believing that someone could be
quite so stupid. Nowadays, with years of experience of humanity behind me, I have no such problems believing that such idiots exist.