5.—(1) Subject to paragraphs (2) and (3) below, the Pensions Ombudsman shall not investigate a complaint or dispute if the act or omission which is the subject thereof occurred more than 3 years before the date on which the complaint or dispute was received by him in writing.
(2) Where, at the date of its occurrence, the person by or in respect of whom the complaint is made or the dispute is referred was, in the opinion of the Pensions Ombudsman, unaware of the act or omission referred to in paragraph (1) above, the period of 3 years shall begin on the earliest date on which that person knew or ought reasonably to have known of its occurrence.
(3) Where, in the opinion of the Pensions Ombudsman, it was reasonable for a complaint not to be made or a dispute not to be referred before the end of the period allowed under paragraphs (1) and (2) above, the Pensions Ombudsman may investigate and determine that complaint or dispute if it is received by him in writing within such further period as he considers reasonable.