The facts are not entirely clear from what is set out. It appears that a property was held by a company owned by a trust and a decision was taken to wind up the company, no doubt with good reason given the introduction of ATED and other drawbacks with this structure. The life tenant of the trust purchased the property out of the company, and HMRC are contending there was a benefit in kind charge whilst the company owned the property.
We are not told the basis for HMRC's suggestion although they have no doubt explained it in correspondence. It might be a question of whether or not the benefit arises from an employment so that the charge arises under ITEPA. Was the life tenant a director of the company? I suspect not, but the charge can also arise if the benefit is provided to a member of a director's family, but then the charge would be on the director not the family member. Perhaps HMRC is arguing that the life tenant is a shadow director of the company in that the directors are accustomed to following her wishes. On this point a case to look at is Secretary of State for Trade and Industry v Deverell  Ch 340 which regrettably gave quite a wide interpretation to the term shadow director. There is also Holland v HMRC 2010 WLR 1 2793. But given that the trustees must administer the trust assets for the benefit of all beneficiaries, and not just the life tenant, I would be reluctant to agree a shadow director situation.
Or perhaps there is some other reason for the suggested tax liability! More information would be helpful.
M B Gunn & Co Ltd