Re: Yes, blame the tool
All the weighting certainly WAS on the Substitution clause, but all of the articles I have read (E.g. Qdos, ContractorUK etc) have said this goes against all the examples they are aware of with case law precedent, as there is also a heavy weighting on SDC (Supervision, Direction and Control).
HMRC also seem to place a lot of weight on using your own equipment, which I have long maintained should be explicitly stated as an exception for IT Professionals. It's fine for plumbers and electricians, but there are few situations IT Professionals would be allowed to use their own laptops, at least for those working on site.