Usufruct over English land

I am dealing with a Dutch Will which is valid under 1963 Wills Act and governs the worldwide estate including English land. Testator was Dutch domiciled at the time of execution but later became English domiciled. The will purports (according to the translation) to give the spouse a “right of usufruct over my whole estate … commencing with my death and ending with remarriage or death of the usufructary”. The Will goes on to say that the estate passes to the legal heirs “in accordance with the law” subject to the obligation to honour the usufruct legacy, for sharing “as specified by the law in force on the date of my death”.

I would welcome members’ comments on what would be the result of purporting to give a usufruct over English land. Would the legacy simply be void and pass instead to the legal heirs?

I will also need to refresh my knowledge on which law would apply to determine the identity of the heirs. I am familiar with the normal movable/immovable distinction leading to law of domicile/situs but this is not simply a question of which country’s intestacy laws apply but a question of interpreting the actual wording used in the Will (i.e. which “law” is meant by this clause?). I expect there is a difference between the law which testator intended to apply to identify legal heirs (presumed to be Dutch law as law of domicile at the date of the Will in the absence of contrary indication) versus the law which actually applies to the devolution of her estate (English law). I believe a Will is interpreted in accordance with the law intended by the testator.