S 143 and deeds of variation

I understand it is possible to include in a will a precatory trust legacy to someone who is not otherwise a beneficiary under the will (currently or as varied) asking them but not imposing a binding trust to make a gift to a charity, and if they do so within 2 years of death, s 143 will read it back into the will for IHT purposes. I understand that for Income tax purposes, gift aid may be available as there is no benefit to the legatee in making the gift to the charity.

Is it possible to do this by a deed of variation with the same effect?

Susan Midha
Inheritax Limited