just pondering on rings and spurs (for 13A).
Now to my simple mind a ring supports more load (or whatever the correct term is) because the electrons can go either way round the ring and don't bump shoulders as much.
A spur off a ring carries less load because there is only a single route for the electrons.
Now if you (for the want of a better description) add a ring as a spur, do you have a chain or just an unusual ring?
i.e. if you break into a ring (assume chopping into a straight run of cable, leaving two ends, 'ring in' and 'ring out'), and instead of taking 'ring in' and connecting it to the start of your new ring, and in a seperate junction box take 'ring out' and connecting it to the end of your new ring, you just connect all four cable ends in a single junction box.
You then have a physical 'figure of eight' configuration.
Is this a logical ring?
Or is this just a fancy spur because of the loading on the connections in the junction box reduce or undo the benefits of having a ring?
In some ways a trivial query, but it does save on one junction box :-)