Before being derailed by whether Thatcher was working-class (!) I looked at the Laurie Magnus letter. The key section is:
... having reviewed it, I would draw four conclusions:
a) Ms Rayner was open about the existence of the Trust and considered that, between them, the firms advising her had appropriate knowledge and awareness of the details and circumstances of the Trust;
b) on the basis of the advice she received, Ms Rayner believed that the lower rate of SDLT would be applicable; indeed she was twice informed in writing that this was the case; but
c) in those two instances, that advice was qualified by the acknowledgement that it did not constitute expert tax advice and was accompanied by a suggestion, or in one case a recommendation, that specific tax advice be obtained; and
d) if such expert tax advice had been received, as it later was, it would likely have advised her that a higher rate of SDLT was payable.
(I added the underlining.)
It sounds as if the tone of the advice was more along the lines of 'this looks fine to us but of course you should get specialist advice'.
That feels quite different to a stern warning that 'we are of course not tax specialists and we warn you to seek specialist advice'.
If I had got that type of advice twice, I would have made exactly the same mistake, even though the stakes were so high. Many of us work on the position that two professional non-expert opinions provide enough reassurance - for all sorts of questions.
The tone of Magnus' report is much, much more sympathetic and regretful than I had realised, or expected. He concludes that in the end, she was responsible for making sure she wasn't relying on 'professional vibes'.
People with professional training probably do have more insight into how much service you're getting, or what the caveats mean in practical terms, and when to trust in professional advice and when to push a bit further. It's sad.