Here I continue from the discussion here, as it was drifting a bit off-topic for that picture there...

@FSB: But the fuse is only to protect the cord and it's connectors, not the appliance itself. So the advantage of using low current fuses is just the possibility to use really thin cord (below 0.5mm^2 or 0.5mm^2 for up to 5A with up to 8A fuse) for an appliance not requiring as high current.
But the insulation has to be thick anyway, so that advantage is rather marginal.

Normally, even the 0.5mm^2 cord is well protected against a short circuit by the B16A breaker normally used for the sockets

What could be a bit more of an advantage is the possibility to connect two high current (up to the 13A) appliances on one place and use them at the same time, as the feed circuit breaker could be 32A. With systems without the fuses in sockets (so using the B16A breakers) you will have to wire two branches with separate breaker for each of them. But that is not as common, usually you do not need them at the same time (e.g. a washer and dryer most likely won't be operated both at the same time).

Washers and driers would be unlikely. More probably is having a couple of 3kw electric heaters going with other light loads.

Couple of 3kW electric heaters in sockets? You mean heaters used normally, or just for an emergency when the main home heating system fails?

Here the main heating system, as well as hot water equipment should be build within the house as fixed installation, regardless if it is solid fuel, electric, water, gas, or recently with passive houses just heat recirculation. Any house without such system can not be certified for dwelling use, so there is no need for socket for the heaters. So the sockets are used just for portable heaters, but portable unit is not often used more than one for some special purpose.

And the things like sockets for expected high current appliances (stove and/or oven in the kitchen, washer/driver) are required to have their separate breaker.

And for installations like shops or such working rooms it is recommended to have separate CB panel for that shop anyway, with each socket separately protected, both overcurrent, as well as RCD's - so failure of one instrument does not affect the others, as well as having the possibility to switch them OFF independently

Sorry I should have been more specific. After world war 2, when the ring circuit was introduced, home heating was either a coal fire in an open hearth or portable parafin heaters. Gas Central heating didn't exist and bar type "electric fires" became very popular for main heating. The ring system was designed to reduce the use of copper whilst allowing a couple of such heaters whilst allowing other loads like lamps and radios ect. Not anymore though. But we have the wiring system, it works, we have a very thourough set of regulations so why bother changing it.

Here's is an example:
http://galleryplus.ebayimg.com/ws/web/221344623667_1_0_1/1000x1000.jpg

That could be the reason, indeed.

Of course, once some system is in use for long time, become wide spread and does not create really excessive problems, no one will change it, anywhere.
But for today's use of high amount of low power devices the massive plugs become really a highly impractical. I would be surprised, if newer codes won't allow the use of some way more compact socket/plug systems (with appropriate wiring and protection), moving the system there (and keep the large plugs just for the high current devices)...

Such "bar heaters" were popular here as well, but just as a supplementary system. The main heating were coal/wood (and sometimes really everything what burns, but that is another story) fired stoves, lately replaced by gas heaters and/or central heating.
The electricity was here too expensive to use it for such direct heaters, the only somehow usable method were accumulation heaters, able to suffice with the cheap "nighttime" tariff. And these were really high power input devices, because they had to "charge" for the full day operation over less than 6 hours, so use fixed wired 3-phase power, usually about 8kW per room.
The direct heating (without the accumulation, so the power input scheduled by the grid operator) was even not allowed as the main building heating system I think even till 1990, the reason was to avoid problems with grid stability...

What the (...) is this about? As a maintenance engineer working with circuits I've never come across any problems with ring mains. You occasionally get a incomplete ring picked up on a periodic but no problems what so ever, TBH there is so much "spu" here i can't be bothered to read it all!