Nil Rate Band Discretionary Trust and the Transferrable Nil Rate Band

I am dealing with an estate where there is a NRBDT in the Will of the deceased. He held minimal assets. However, surviving W has significant assets.
Would I be overcautious to Appoint Out the assets held in the NRBDT (DoV can’t be used due to the wording of the trust and the class of beneficiaries) to preserve the TNRB.
I can’t find out with certainty whether the NRBDT blocks the TNRB to W regardless of whether the deceased had assets of up to the threshold or not.

I believe whatever value of the estate passes into the DT will use up part of the NRB. The surplus amount would be regarded as unused and therefore available to transfer to wife. (So if the deceased’s estate was valued at £162,500 then 50% of the NRB remains unused and is available for wife.)

Ihsan Ali
I Will Solicitors Ltd