An employee who wishes to claim that they have a right under the Equal Pay Act 1970 (EPA) to be paid the same as a co-worker of the opposite sex has to show, amongst other things, that they and their co-worker are engaged in either like work, or work that has been rated as equivalent in a job evaluation study (JES), or work of equal value. A claimant who shows that she and her comparator are engaged in like work or work of equal value is entitled to claim back pay for up to six years from the date the claim is brought (provided the jobs remained the same throughout the earlier six-year period). A question raised in this appeal was whether the same principle would enable employees who are basing their claim on the ‘work rated as equivalent’ ground to claim back pay for a period pre-dating the implementation of the JES. In other words, does a JES have retrospective effect for the purposes of equal pay liability? In the Bainbridge case both the tribunal and the EAT said that a JES does no