Trustee acting ahead of Grant

The deceased has left a Will with the following key elements: -

2.1) I appoint surviving spouse A as my executor; but

2.2) if she is unwilling or unable to act then I appoint daughter B instead.

… In this Will, the expression ‘my trustee’ means (as the context requires) those of the executors who obtain probate and the trustee for the time being of any trust arising under this Will.

Residue

5) I give to my Trustees my estate and property over which I have a general power of appointment to hold it on trust to pay my debts, taxes, legacies and funeral and testamentary expenses and to hold the residue on the trusts declared in the rest of this clause… (discretionary trust)

STEP Provisions (2nd edition) & Special Provisions apply.

Surviving Spouse A has started to intermeddle in the estate and therefore is acting as executor.

The use of a Discretionary Trust for Residue is providing the flexibility and protection against spouse’s care fees that the testator required. However, growth in the value of the estate in the years between attestation and death mean that initially the estate is liable for IHT, which will need to be paid pre-grant. Hence the family are looking to make appointments of trust assets within 2 years to reduce IHT to zero.

But, given the specific wording in the Will of the trustee definition, is there a basis for A to act as trustee and make suitable appointments ahead of the Grant, thereby avoiding the overhead of having to fund payment of IHT followed by subsequent reclaim? Clearly, in any event spouse A is trustee once the Grant is obtained. I can emphasise that beneficiaries of the discretionary trust are onside with the intended appointments.

Thank you for any and all input.