My understanding is that an entailed interest can only be “barred” once the interest in tail has arisen.
On that basis, is the current beneficiary the original life tenant, or a “tenant in tail” – i.e. one whose interest arises under the entailing provisions?
If the current beneficiary is not a tenant in tail, my understanding is that whilst a disentailing deed may be executed now, the absolute interest will not arise until after their death. However, if the current beneficiary is a tenant in tail, then a disentailing deed may be of immediate effect.
Due to the rarity of entailed interests, and the risks of getting it wrong, I suggest an approach to counsel at Lincoln’s Inn both to confirm the effect of the execution of a disentailing deed on the trusts as they now stand, and to draft an appropriate deed.