30.1 Subject to the following provisions of this Rule, a Member of the NATS Section may elect not less than 28 days before the date when any pension becomes payable to him from the NATS Section to surrender the whole or a proportion of his pension from the NATS Section which exceeds the Guaranteed Minimum Pension in respect of him in order to provide a non-commutable and non-assignable pension payable after his death which in the opinion of the Trustees on the advice of the Actuary is equal in value to the pension so surrendered.