(1) This rule applies if an active member is seconded during any period—
(a)to the United Nations or the North Atlantic Treaty Organisation, or
(b)under arrangements with any other organisation or person under which persons who are in service as a result of which they are eligible to belong to the Scheme are seconded into other service.
(2) If at the end of that period the member resumes service in the armed forces in which he is an active member of the Scheme, he may opt to make a single lump sum contribution to the Scheme to increase his reckonable service by an additional period equal to the length of his secondment.
(3) The option may only be exercised by notice in writing to the Scheme administrator in such form as the Secretary of State requires.
(4) If a member exercises the option under paragraph (2) and pays a contribution equal to the aggregate amount of—
(a)any contributions returned to him by the pension arrangement to which he belonged in respect of his service during the secondment, and
(b)any lump sum paid to him on leaving the organisation or to the person to whom he was seconded as a severance payment,
the member is entitled to count the period of his secondment as reckonable service.
(5) If the aggregate amount mentioned in paragraph (4) is less than the amount determined by the Scheme actuary to be the amount required to be paid in order to increase the member’s reckonable service by the period of his secondment, the Secretary of State must make a contribution to the Scheme equal to the difference.