Section 15 of the Wills Act 1837 (WA 1837) states: '...if any person shall attest the execution of any will to whom or to whose wife or husband any beneficial devise, legacy, estate, interest, gift, or appointment, of or affecting any real or personal estate (other than and except charges and directions for the payment of any debt or debts), shall be thereby given or made, such devise, legacy, estate, interest, gift, or appointment shall, so far only as concerns such person attesting the execution of such will, or the