@steely_glint Ring “main” (more correctly called ring final) circuits are a weird UK thing brought about by copper shortages in the early post-war (WW2) years plus a conviction on the part of planners during the war that post-war house heating would be mostly use electric powered by nuclear. Almost nobody else bothers with them.
AIUI, they're becoming less common now in new build even in Britain which is, IMHO, a good thing as, if they were ever used at the power levels they were originally designed for, would be intrinsically fail dangerous.
If you're actually using the power delivery capabilities provided by the two paths to a group of sockets but there's a break in one side of the ring the devices will appear to continue to work but the half ring will be overloaded. Luckily, in real life it's very rare to draw enough power for that to actually matter.
@crablab