Went to install a few extra sockets into dado trunking in an office, nice easy one for a saturday morning. Checked ring continuity at first socket to tap into ring, no continuity, went on to discover spurs off spurs big style, 6 sockets spurred off ring on one side of office, 7 spurred off ring on other side and two spurred off other side, all installed by an niceic approved contractor. This wasn't picked up on a recent periodic either.