Provided nevertheless, that in cases where it shall be certified in manner herein-after mentioned that for ten years now last past it hath been the usual practice (such practice having in the case of a corporation sole commenced prior to the time of the person for the time being representing such corporation) to renew such leases for forty, thirty, or twenty-one years respectively, at shorter periods than fourteen, ten, or seven years respectively, nothing herein contained shall prevent any archbishop, bishop, ecclesiastical corporation sole or aggregate, dignitary, canon, prebendary, spiritual person, . . . F1 from granting a renewed lease conformably to such usual practice; provided that such usual practice shall be made to appear to the satisfaction of the archbishop of the province in the case of a lease granted by such archbishop or by a bishop, and in the case of a lease granted by any other corporation or person to the satisfaction of such archbishop and also of the bishop having jurisdiction over such corporation or person, and shall before the granting of such lease be certified in writing under the hand of the archbishop in the one case, and of the archbishop and bishop in the other case; the certificate so signed by an archbishop only to be afterwards deposited in the registry of such archbishop, and the certificate so signed by an archbishop and also by a bishop to be afterwards deposited in the registry of such bishop; which certificate shall be conclusive evidence of the facts thereby certified.