Looks like Yahoo lifted it from the
Mirror, or vice versa - but in the Mirror's version:
the 52-year-old has admitted that the father of the electrician responsible for the work drove 50 miles from London to Sittingbourne, Kent to apologise for his "unqualified" son's work.
Which doesn't specify what counts as qualified though - would be interested to see if a Part P notification has been done..
Does also suggest that some of the issue was the existing installation - so maybe no RCD on that circuit, or cpc was used but not properly tested to see if it was connected.
However, if it really was the fixing screws, SparkyNinja, who's opinion I value, thinks that fixing screws aren't 'extraneous conductive parts' because of the small area exposed to touch, so that metal back boxes don't need to be earthed separately (though still good practise)
If it was a plastic back box, maybe the live ended up touching the screws because of the gap between tiles and the back box, since usually the screws are fully enclosed in plastic....
Which raises an interesting question - are tiles considered part of the 'enclosure' when they are thick and there is maybe 10mm gap between the front of the tiles accessory against the tiles and the front of the back box.
Edit:
This bit may be relevant (from the Mirror)
Despite this, when a second electrician came to fix the problem, he flagged multiple harmful issues - including the fact that live conductors were not made safe, and some were still live
Which could mean almost anything - but perhaps a circuit from the original room was just cut off and left in the wall, touching a back box? Or maybe that was just additional issues found when the installation was checked....
Would like this to be investigated by the HSE and a report issued, but no doubt Wickes will do anything possible to avoid that and it won't happen since there was no serious injury.