Are you perhaps confused by the term 'trustees' The executors are themselves trustees and are sometimes referred to as that in phrases like 'the trustees of the estate of X deceased'. They hold the deceased's estate, as owners for the time being, for the benefit of the beneficiaries under the will. That ends when all taxes have been paid on it, the deceased's property has been distributed, and all the terms of the will complied with.
But the fact you ask suggests that you'd best get professional help from a solicitor