Why did the UK change from round pin to square pin plugs?

To keep people in work.

No. Because it is easier to manufacture a true pair of self-wiping contacts that cover a wide area, against a flat bar, than against a round pin.

the 13A design was all about safety, not jobs for the boys. That came later, with the labour governments.

There were multiple reasons for the move to BS1363 square pin system. The old round pin system was recognised in the 40s to be thoroughly inconvenient, inadequate for increasing numbers of appliances, unsafe and frankly insane. It was a whole pile of unnecessary problems by design, plus there were lots of unsafe plugs, sockets, adaptors etc in use.

At the heart of the square pin system was the ring circuit. It enabled unlimited sockets to be fitted on just one ring of cable, on 1, 2 or 4 fuses. This was a huge money and material saving over a round pin radial setup with the same number of sockets, which mattered after the war. Also old 15A radials could be upgraded to add unlimited sockets relatively cheaply.

To put existing round pin plugs on such circuits is not safe. A lamp with a bellwire or speaker wire mains lead on a 2A plug & socket on a 32A fused ring is not ok. If the same sockets were used, this would be the inevitable common result. A different plug system was needed.

The new plug system was designed to be far safer than the crazy round pin system. It also had the desired effect of gradually taking all those round pin hazards out of service. If you've ever used round pin kit you'll know how bad it often was. Kicking plugs to get the pins to make contact was common practice for example. There were wooden plugs & adaptors, some with touchable live tubes. Irons & heaters on BC plugs were common etc.

IMHO it's time today to revisit the system to improve it a bit. 2 pin BS1363 variant moulded-only plugs could be added, enabling use of 3 appliances per single faceplate, 4 or 6 per double.

I don't disagree with what you say. I like the system.

However, if the argument was as persuasive as this, why did other countries (with minor exceptions) not follow and why is Schuko and its variants so widely used today?

The ring system has clear advantages on cost & safety, yet close to no-one outside the UK understands how it works or what its upsides are. I find that strange but there it is. Our plugs are bulky compared to most countries, and using radials they don't need the plug fuse, so ours don't suit radial systems particularly well. And ours are a hazard to feet.

I am still finding it difficult to follow the concept of radial circuits. If there are 10 sockets in the kitchen, does each have its own cable run to the consumer unit and its own fuse there? Do all the cables run in a single conduit of does each run separately? This would require a maze of cabling and a vast number of fuses.

I suppose the way round it would be to have one main socket and lots of extensions, but this would be less safe than our system. How would the user know which was the main socket for high current appliances? Two appliances could bring down a 16 amp fuse.

Take a look at a domestic American 'breaker panel'. Yep, they have a ton of breakers. I think they get 2 or 3 sockets per radial, but not sure on that point

It is nothing like that low.

Capitalism.

It's interesting that the panel is often situated in a very easy to get at place. Suggesting trips are commonplace.

In fact trips are not commonplace in the USA or Canada.

You live there, then? Aren't you Wodney under yet another alias?

Just why would you stick a breaker panel in the middle of a living room wall if you rarely needed to access it?

Don't need to. We have this funky system called usenet where we can ask others in different countries about how often they see stuff like that happening.

Why do you believe that that is common there ? Have you lived there ?

Do they tell the same lies as you, Wodney?

Thought you knew how to use usenet, etc. You lied about that too, then?

You never could bullshit your way out of a wet paper bag.