If T signs by way of mark or amansuensis signs for T it must be in the presence of a Commissioner of Oaths. They must then issue a certificate acknowledging that they regard the signed will as the valid will for T and they are satisfied of the identity of T. The Certificate must be attached ASAP after will is signed. If will is longer thsn one page COO must sign the will on every page excl the page where certificate is. May also sign anywhere.
If T dies before certificate is attached, it is still fine it must just be attached asap. The certificate can be attached to any page of the will.