If the legal title is in the name of the deceased, a grant will be required to be able to transfer it to another party.
If the property is subject to a life interest in favour of the deceased’s son it would appear the deceased may have been a trustee of the land, in which case you will need to see the trust instrument to identify who has the power to appoint new trustees. If the deceased as the last trustee, then the power to appoint passes to his personal representatives.
As the property title is in the name of the deceased the land is unlikely to be subject to the Settled Land Act, but the position will be apparent after a review of the relevant trust instrument. In any event, if it is the son who is entitled to the life interest, it cannot be settled land within the estate of the deceased.
If the deceased was the person who settled the property, was this more than 7 years ago and, even if it was, have they retained any rights to it which might give rise to a reservation of benefit for IHT purposes?