(2)As between immediate parties, and as regards a remote party other than a holder in due course, the delivery—(a)in order to be effectual must be made either by or under the authority of the party drawing, accepting, or indorsing, as the case may be:(b)may be shown to have been conditional or for a special purpose only, and not for the purpose of transferring the property in the bill.But if the bill be in the hands of a holder in due course a valid delivery of the bill by all parties prior to him so as to make them liable to him is conclusively presumed.
