 Some authors place fully secret and half-secret trusts in different categories, including Alastair Hudson and Lionel Astor Sheridan.To this it has been argued that, if the "outside the will" theory is the true basis for the secret trust, whether the mention of the existence of the trust on the face of the will should affect its nature.In Hudson's opinion, fully secret trusts are constructive trusts, because they exist to prevent fraud.