MELBOURNE (Standard&Poor's) Sept. 23, 2003--Standard&Poor's Ratings Services said today that it has assigned its 'A' long-term rating to National Australia Bank Ltd.'s (The National; AA/Stable/A-1+) £400 million trust preferred security issue. The underlying 49-year subordinated debentures, issued by The National's London branch, convert to preference shares of The National upon the occurrence of a specified trigger event. This feature supports the ability of these securities to absorb losses and achieve regulatory treatment as Tier 1 equity. The bank guarantees the payment on the trust preferred securities, where a payment has been made on the underlying debenture. "The trust preferred security is rated three notches below the senior rating on The National, reflecting its subordinated nature and