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A half secret trust is a trust declared in a will where it is clear that property is left on trust but the terms of the trust are excluded from the will. For example, "£50,000 to Eliza on trust". The House of lords upheld the validity of a half-secret trust in Blackwell v Blackwell [1929] AC 318 where obiter dicta by Viscount Sumner have been used to support the view that communication of the trust and its terms must take place before or at the same time as the execution of the will.