When we install a ring final we usually ensure that all points are on the ring itself, that way it means that one point (twin or single socket for example) may be added directly to any point on the ring as an unfused spur, instead of adding at the point itself we could choose the option of adding by putting a junction box to any cable bridging two joints, we may also add one such spur at the origin (the fuseway) that is pretty standard as a ring final layout.
It is considered good housekeeping to not have more sockets on spurs (one length of 2;5 cable from any socket on the ring to one socket spurred from the ring) on any ring final circuit.
In any case each cable and connection must be robust both mechanically and electrically for the lifetime of the ring circuit.
Spurring only from points on the ring makes it easier to achieve this and to inspect it periodically as appropriate.
To extend any ring by keeping it as an actual ring without spurs has it merits but we must test that sensible ring total lengths are still maintained and not exceeded, that can be sometimes not easy to ensure and really requires proper test gear.
I myself have always endeavoured to make a quick approximation to see that a ring total length of 88 metres will never be approached on any ring and my target total max would try not exceed around 60 or 65 metres in any system, accordingly no spur length is allowed to be more than say 3 metres anywhere on the ring (I use the concept of a 2m max otherwise extend the ring not spur from it).
Junction boxes if used should be in accessible places (how accessible to be considered as accessible rather than inaccessible well opinions vary), I only consider easily accessible as accessible personally and that is why I prefer spurring or extending the ring from existing points as the preferred option.
I also give some consideration to achieving an approximate balance around a ring as regards load and duration of loads - more a quick sketch on the back of a fag packet sort of a thing rather than detailed calculations.
What I do wince at is when I see is what I consider a pretty radial type circuit with the last point or so having a longer length of cable back to the fuseway, it is a bit daft in my opinion because there is not much merit in it if any.
Again, pack of a fag packet style, the initial aim should be to spread the load evenly around the ring (again by actual estimated loads and duration of such) or alternatively most of the load around the middle one third of the ring or a combination of both ideas.
There are some that favour, if spurring from the ring directly from the cable rather than at a point, to carefully splice open the without damaging the conductors and neatly put all three under the grubscrews (or double them under tunnel terminal types) without breaking the conductors and then adding just the new spur end to that connection, that has the advantage of minimising possible problems caused by loose connections, so that has some merit too, is is more difficult to add earth sleeving for identification purposes on the ring proper parts of the earthwire, it is not considered for insulation properties of the earthwire although, fortuitously, it might add a bit, conductors kept neatly spaced inside joint enclosers is key really,
From the outset a new ring (or radial) circuit should be configured as providing adequate points by numbers and locations and additions/amendments as unlikely exceptions because things have changed unexpectedly during the life of the circuit, that is down to good design but it might, unfortunately, be impacted by economics at the time of design.
If I saw a ring with less (or none at all) points on the ring itself and more or all of the points on spurs I would not automatically condemn it )But I would not actually like it), similarly with more than one spur from the fuseway and mo ring involved, providing that all connections are mechanically and electrically sound. Example - If I was to see a 30A or 32A circuit with 5 or 6 short radials each to one twin socket, that would not magically become "dangerous" although it would break the regs, if done properly, I would certainly look at it twice though.
If you show a ring with spur at the fuseway then remove the ring itself from the fuseway and just leave one radial with one twin socket as the circuit then it is amazing how many (including some electricians) would condemn it as actually or potentially dangerous for some reason, ask them why and they cant give you a reason.
Tin hat on and ducked below the parapet !
