As Paul Saunders indicates, a trust with a single beneficiary who is also the settlor is not impossible or prohibited as such.
There is also authority that a trust with a single beneficiary cannot be a discretionary trust for tax purposes, obviously enough. Arguably such a trust is always effectively revocable under the rule in Saunders v Vautier but the extent of the powers given to the Trustee/Protector may need to be considered. The effect of such a trust may be to give powers of management to the Trustee so the beneficiary can claim to be uninvolved in the management of the trust assets (which is the rationale behind “blind trusts” to which Paul refers). How realistic that claim is and how consistent, if true, with the duties of the Trustee in such a case is another matter. In England a trust which is in substance a will but created by an instrument which does not comply with the formalities required for a will is likely to be invalid. Depending on the motive, there may well be a better way of doing things than the kind of trust you mention.
Mark Hubbard
New Square Chambers