" (1) A person (A) discriminates against another (B) if A applies to B a provision, criterion or practice which is discriminatory in relation to a relevant protected characteristic of B's. (2) For the purposes of subsection (1), a provision, criterion or practice is discriminatory in relation to a relevant protected characteristic of B's if— (a) A applies, or would apply, it to persons with whom B does not share the characteristic, (b) it puts, or would put, persons with whom B shares the characteristic at a particular disadvantage when compared with persons with whom B does not share it, (c) it puts, or would put, B at that disadvantage, and (d) A cannot show it to be a proportionate means of achieving a legitimate aim. (3) The relevant protected characteristics are— … sex …"
"On a comparison of cases for the purposes of section … 19 there must be no material difference between the circumstances relating to each case."
"particular disadvantage"
"[24] The first salient feature is that, in none of the various definitions of indirect discrimination, is there any express requirement for an explanation why a particular PCP puts one group at a disadvantage when compared with others … … [26] A third salient feature is that the reasons why one group may find it harder to comply with the PCP than others are many and various … They could be social, such as the expectation that women will bear the greater responsibility for caring for the home and family than will men … … [27] A fourth salient feature is that there is no requirement that the PCP in question put every member of the group sharing the particular protected characteristic at a disadvantage … … [28] A fifth salient feature is that it is commonplace for the disparate impact, or particular disadvantage, to be established on the basis of statistical evidence … … [29] A final salient feature is that it is always open to the respondent to show that the PCP is justified – in other words, that there is a good reason for the particular … requirement … The requirement to justify a PCP should not be seen as placing an unreasonable burden on respondents. Nor should it be seen as casting some sort of shadow or stigma upon them. There is no shame in it. There may well be very good reasons for the PCP in question …"
"There is no formula for identifying indirect discrimination pools, but there are some guiding principles. Amongst these is the principle that the pool should not be so drawn as to incorporate the disputed condition."
"In general, the pool should consist of the group which the provision, criterion or practice affects (or would affect) either positively and negatively, while excluding workers who are not affected by it, either positively or negatively."
"In other words, all the workers affected by the PCP in question should be considered. Then the comparison can be made between the impact of the PCP on the group with the relevant protected characteristic and its impact upon the group without it … There is no warrant for including only some of the persons affected by the PCP for comparison purposes …"