GB wrote:
If there is a break in the circuit, all the sockets may still work. The
circuit breaker won't trip. Yet one arm of the ring is taking all the
load that's meant to be divided between the two. Isn't that going to
lead to overheating?

That's why one of the installation/periodic review tests is to test ring
continuity - you test the continuity going into one end of the ring and
coming out of the other end of the ring.

I've got new tenants moving into my shop so have done my usual intra-tenant
testing, and still passes fine after being re-wired in 1997. I did my Mum's
house a few years ago which was rewired in the 1970s, also perfectly happy.
How is a cable likely to break is it never moves?

jgh