Isn't it possible that the leg going under the floor is one of the ring final legs, and one of the others that goes up is the other, then the remaining two are spurs or another ring final.
Simple test, is power off, disconnect, and untwist the ends - then check for continuity between every wire and every other wire. That you provide clues of which wires are part of a ring, and which ring.
Twisted 2.5mm, suggest a quite amateur DIY job.