Accordingly, a trustee de son tort is not a person who is formally appointed as a trustee, but one who assumes such a role, and then cannot be heard to argue that he did not owe fiduciary duties.
Lewin on Trusts [1] says at 42-74: If a person by mistake or otherwise assumes the character of trustee when it does not really belong to him, he becomes a trustee de son tort and he may be called to account by the beneficiaries for the money he has received under the colour of the trust.
A delegate, in such circumstance, has done no "wrong" and is not intermeddling in the trust and so does not become a “trustee de son tort”.
It would cause considerable surprise in the industry if such a company was to find itself designated a trustee de son tort.
Because it was common practice it was important that an authoritative decision be given as to whether such an administrative company should be treated as a trustee de son tort.