The Claimant had retired after working for 27 years. Her full-time equivalent (“FTE”) service, taking account of periods of part-time working, was 21 years (she'd worked part-time after the birth of her daughter). The Claimant’s particular complaint was that, whereas a full-time worker who had worked 20 or more years as at the Normal Retirement Date would be entitled under the Scheme to the maximum available pension of 2/3 of final salary, she was only entitled to 21/27 (about 78%) of the maximum pension notwithstanding the fact that she had more than 20 years’ FTE service. The Claimant contended that the Scheme amounted to double pro-rating in the case of those with some part-time service and put her at a particular disadvantage.

Indeed, when approaching retirement, the claimant had been told by the pension scheme administrators that she would receive a maximum total yearly pension of £69,726.59. That sum was then revised downwards to a new estimated benefit of £52,798.96.
The pension scheme benefits depended on the date and age at the date of entry into the scheme. The correct comparator was, therefore, a full-time worker who started on the Scheme at the same age and on the same date as the Claimant. The Claimant’s suggested comparator would have failed to take account of a critical feature of the Scheme which was that accrual rates depended on the age of joining and the years remaining until normal pension date.

The claimant also argued before the EAT that the tribunal should not have accepted arguments made by the employer after their submissions had been accepted by the tribunal. It may be preferable to have arguments set out at the time of the decision-making process but it is not fatal to a defence to rely on different reasoning later:

"Whilst it seems obvious that a justification that is fully evidenced and which was articulated at the time the measure was implemented would garner greater respect than one put forward a long time after implementation, it is clear from the passages above [in Ministry of Justice v O’Brien [2013] ICR 49] that an employer is not precluded from relying upon a later justification."
http://www.bailii.org/uk/cases/UKEAT/2017/0113_17_0711.html