“3(1) Where any part of [earnings paid to or for the benefit of an earner in respect of an employed earner ‘s employment] … is normally paid or treated under regulation 6 … as paid at regular intervals, the earnings period in respect of those earnings shall, subject to the provisions of paragraphs (2), (2A), (3) and (4) … be the period – (a) the length of which is – (i) in the case where there is one regular interval of 7 days or more, the length of that interval; (ii) in a case where there are regular intervals of different lengths each of which is 7 days or more, the length of the shorter or, as the case may be, shortest interval; (iii) in the case where the regular interval is less than 7 days or where there is more than one such interval, a week; (iv) in a case where there is one or more than one regular interval of 7 days or more and one or more than one regular interval of less than 7 days, a week,; and (b) which is one of a succession of periods of the same length beginning in the case of the first such period in any year on the first day of that year, and in the case of each subsequent period immediately upon the ending of the period which last precedes it. …… ” [15] The pre-1984 form of regulation 3(1)(a) did not expressly cater for a case where “parts” of an employed earner’s earnings were paid at regular intervals but those regular intervals were themselves of different lengths. However, the focus was still on the shortest identified interval at which earnings were paid. In both amended and unamended forms, therefore, the regulation catered for circumstances where an employed earner’s earnings were paid in “parts” at regular intervals. The nature and 6 quality of such “parts” (for example basic salary, overtime, holiday pay or pension contributions) did not matter: the question was simply whether earnings were de facto paid in “parts” and, if so, at what intervals. [16] So far as relevant for present purposes, regulations 19, 21 and 22 further provided as follows:- “19(1) For the purposes of earnings-related contributions, there shall be excluded from the computation of a person’s earnings in respect of any employed earner’s employment any payment in so far as it is – …… (f) any payment of earnings in respect of employed earner’s employment which a secondary contributor is required to make under regulation 3(2)(e) of the Occupational Pension Schemes (Recognition of Schemes)(No 2) Regulations 1973; (g) any payment by way of a pension; …… 21(1) The provisions of this regulation shall not apply for the purpose of any decision of the Secretary of State in so far as that decision relates to contributions based on payments made more than one year before the beginning of the year in which that decision is given. (2) With a view to securing that liability for the payment of earnings-related contributions is not avoided or reduced by a secondary contributor following in the payment of earnings any practice which is abnormal for the employment in respect of which the earnings are paid (hereinafter referred to as an “abnormal pay practice”), the Secretary of State may, if he thinks fit, determine any question relating to a person’s earnings-related contributions where any such practice has been or is being followed, as if the secondary contributor concerned had not followed any abnormal pay practice, but had followed a practice or practices normal for the employment in question. …… 22 Without prejudice to the last preceding regulation, the Secretary of State may, where he is satisfied as to the existence of any practice in respect of the payment of earnings whereby the incidence of earnings-related contributions is avoided or reduced by means of irregular or unequal payments, give directions for securing that such contributions are payable as if that practice were not followed.”