I've just re-sited one of these Varilight 12v lighting SMPS transformers (bought from TLC) and noticed the cover/cord grip on the mains end had actually pierced the insulation of the feed TW&E. Its fixing screws weren't done up particularly tight, either.
The design of the grip is a square section bar which fits tightly between two others if tightened fully.
These designs annoy me. It is presumably designed for ordinary TW&E input
- the instructions say no different - but there is no provision to make off the earth and therefore to extend it onwards if needed - although there are two sets of mains terminals for just this purpose.