Section 18 governs investment in bearer securities, at present permitted to a limited extent and governed by section 7 of the Trustee Act (Northern Ireland) 1958, a provision repealed by this Act. The new provision allows trustees to invest in securities payable to bearer but they must appoint a person to act as custodian, unless their trust instrument or statute allows otherwise. The appointment of the custodian must be made or evidenced in writing.