Secret and half-secret trusts do not meet the formalities set out in section 9 of the Wills Act 1837 but are still enforced by the courts to promote equity, justice and fairness as well as to prevent unjust enrichment and fraud.

These types of trust arise where a testator creates a will but wishes to leave property to a person they do not want to be named. Instead the property is left to a confidant known as a secret trustee who acts as an intermediary.

Whereas a secret trust is not mentioned at all in the will, a half-secret trust is mentioned though the relevant details (such as the beneficiary) are not provided.

According to Ottaway v Norman [1972] there are three things that must be established for such a trust:
1. An intention to benefit the person who cannot be named.
This must be an intention to create a trust obligation rather than a mere moral obligation (McCormick v Grogan (1869))
2. Communication of that intention to the secret trustee.
Communication can be written or oral but must include the intention to establish the trust as well as any relevant terms (Re. Boyes (1884)). These terms include the beneficiary and the subject matter. Certainty of subject matter is important because if funds are added to the trust and that is not communicated to the secret trustee then that addition will not be valid (Re Colin Cooper [1939]). For secret trusts the communication must take place prior to death (Moss v Cooper (1861)) but for half-secret trusts the communication must take place prior to the execution of the will as per Lord Sumner in Blackwell v Blackwell [1929].
3. Acceptance by the secret trustee of that obligation.
Acceptance can be express or implied.

Secret trusts can also arise in cases of intestacy where the testator knows that property will pass to a certain beneficiary on death (Sellack v Harris (1708)).

If the trust fails the property may either simply go to the beneficiary (the proposed secret trustee) or there will be a resulting trust back to the testator’s estate (Vandervell v IRC [1967]).

The rules of evidence can provide major hurdles in the context of secret and half-secret trusts. For example the parol evidence rule prioritises written evidence (such as the will) over oral testimony. Furthermore the standard of proof requires “the clearest and most indisputable evidence” as per Lord Westbury in McCormick v Grogan (1869) because the claim is essentially an allegation of fraud.

In cases of joint ownership where one person knows about the secret trust and one does not then the question is when the person who knew accepted the role of secret trustee. If it was before the will was made then all joint owners are bound whereas if it was afterwards then only the secret trustee will be bound.