“(1) In these rules ‘pensionable earnings’, in relation to a person who is a member, means – (a) permanent pensionable earnings … from the employment in which the person is a member. This is subject to paragraphs (4) and (6). (2) For this purpose ‘permanent pensionable earnings’ means – (a) basic pay, (b) if or to the extent that the Minister has determined that they are to be treated as permanent pensionable earnings for the purposes of these rules, allowances granted on a permanent basis to persons in particular posts or kinds of employment, and (c) anything included by virtue of paragraph (4). … (4) Anything which would not be regarded as pensionable earnings under paragraph (2)(a) or (b) or (3)(a) [which defines ‘fluctuating pensionable earnings’] is to be so regarded if – (a) it is expressly provided to the member on the basis that it is pensionable and was so provided before1st October 2002 , and (b) the Minister has agreed that it should be so regarded, …”