Paragon Finance Plc v D B Thakerar & Co (A Firm)  1 ALL ER 400,  EWCA Civ 1249
In Cunningham v.Cunningham & Others  JRC 124, the court
considered the concept of a trustee de son tort.
The court also quoted from Thomas and Hudson, The Law on Trusts which says at para 30.03:-
In Soar v Ashwell, Lord Esher MR took the view that an intermeddling stranger must be treated, and therefore held liable, as if he were a properly appointed trustee:
- ‘Where a person has assumed, either with or without consent, to act as a trustee of money or other property…a Court of Equity will impose upon him all the liabilities of an express trustee…’  2 QB 390.
The prime liability of the express trustee is not to act in breach of trust, and the trustee de son tort will likewise be held personally liable to account for any such breach. In Particular, if he was wrongfully transferred or dissipated trust property will have to account for it to the trust.
A person who has not been appointed a trustee but intermeddles in the administration of a trust by taking it upon himself to act as if he were a trustee will be held liable as if he were in fact a properly appointed trustee. He is known as a trustee de son tort. The principle was explained by Smith LJ in Mara v Browne  1 Ch 199 :
‘…if one, not being a trustee and not having authority from a trustee, takes upon himself to intermeddle with trust matters or to do acts characteristic of the office of trustee, he may thereby make himself what is called in law a trustee of his own wrong-i.e. a trustee de son tort:
Jasmine Trustees Ltd v Wells & Hind  3 WLR 810,  1 All ER 1142,  EWHC 38 (Ch)
Dubai Aluminium Company Ltd v. Salaam  1 All ER 97,  1 LLR 65,  1 Lloyd’s Rep 65,  3 WLR 1913,  1 BCLC 32,  1 CLC 1020,  WTLR 163,  UKHL 48,  2 All ER (Comm) 451,  2 AC 366,  IRLR 608