My understanding is that the deceased beneficiary’s estate must have been increased by the chargeable transfer in question for QSR to apply.
Normally, the IHT on a failed PET is payable by the recipient of that gift, unless provided otherwise either at the time of the gift or specified in the will (in which case it is a general legacy to the recipient).
As the surviving spouse, the benefit they received was not a chargeable transfer and, even if their entitlement was reduced by IHT on the failed PETs being paid out of the estate, it would be the estates of the recipients of the failed PETs that would be entitled to the benefit of QSR.
Thank you for your comments. HMRC have reverted to me on this today and they inform me that QSR is available on the failed PET under s.141 of the IHTA 1984.
I have not yet looked at this, but will let you know the outcome of my investigation.