Effect of peppercorn lease in Will

I have a Will from 1971 which contains the following:

“I devise to my Trustees my house … upon trust that my Trustees shall if my son A so desire let the same to him on a yearly tenancy at a rent of One pound per annum without power for him to assign, sublet or part with the possession of the said premises and upon condition that he shall keep the said premises in good and tenantable repair and insured against all damage by fire and other normally insured risks PROVIDED that so long as he shall duly observe and perform the conditions aforesaid a notice to determine such tenancy shall not be effectual unless signed by all my Trustees for the time being but after any default on his behalf in observing and performing the conditions aforesaid such notice shall be effectual if signed by my Trustees other than my said son A”

Then:

“to pay one half of the proceeds of sale of my said house … if and when it shall be sold to my said son A and to pay the remainder to my other sons B and C equally”

I am dealing with the estate of one of the other two sons, B.

My query is - what is the effect of this clause from an IHT reporting point of view for B’s estate?

Susan England
Parry Law Solicitors