Revert to Settlor rules

I have a trust which was created in 2003 when three settlors reverted assets onto a life interest trust for their mum. On the death of the mum, the assets then revert back to the settlors. I understand that as the settlors retained an interest in these assets it was a GWROB and therefore 1/3 of the trust assets is included in their estate for IHT purposes. They are also taxed on 1/3 of the trust income under the settlor interested rules.

One of the settlors died last year, therefore I understand there is a IHT charge on his 1/3 share of the trust assets.

As the assets will remain on trust for the deceaseds mum until she dies (before reverting back to his family), is this 1/3 share of the assets now under the relevant property regime, or a QIIP for the mum as the trust was created before March 2006.

Any comments would be greatly appreciated.

QIIP. I don’t see why the death of the settlor would have affected mum’s pre-2006 IIP so it just continues as before - outside the relevant property regime.