In most cases, the obligation is to make some inter vivos transfer of property but in Ottaway v Norman [1972] Ch 698, the doctrine was held to apply equally to an obligation to make a will in favour of the secret beneficiary. The testator left his freehold bungalow to his housekeeper. It was agreed between them that she would devise the bungalow by her will to the testator’s son, which she failed to do. The court held that the son was entitled to the bungalow on the basis that the obligation was imposed and accepted and the means of carrying out the obligation was immaterial. Brightman J said:

I am informed that there is no recent reported case where the obligation imposed on the primary donee is an obligation to make a will in favour of the secondary donee as distinct from some inter vivos transfer. But it does not seem to me that that can really be a distinction which can validly be drawn on behalf of the defendant in the present case. The basis of the doctrine of a secret trust is the obligation imposed on the conscience of the primary donee and it does not seem to me that there is any materiality in the machinery by which the donor intends that obligation shall be carried out . . .