Yesterday’s Supreme Court decision has removed one key hurdle blocking the progress of equal pay claimants wishing to select male comparators working for the same employer but at different establishments. It has said that such a comparison is possible even if in practice those men would never be employed to do their current jobs in the same place as the women.

This case involves 251 classroom assistants, support for learning assistants and nursery nurses employed in a local authority’s schools. They wish to compare their terms and conditions with various male manual workers (eg groundsmen and refuse collectors) based at a number of depots in the local authority’s area. Given that the men were employed at different “establishments” the claimants needed to show that “common terms and conditions” were observed both at their place of work, and the various establishments where their chosen comparators worked.

This would have been no problem if both sets of employees had been subject to the same collective agreement. However at the time of the claim the claimants were employed on “Blue Book” terms whereas the men were subject to “Green Book” terms. The tribunal had therefore asked itself, in the hypothetical scenario that the men were employed at the women’s establishment, whether they would have been engaged under Green Book terms. It concluded that they would have been. The Supreme Court said that this was exactly the right question to ask, and it was entitled to reach the answer it did. There was no room for imposing additional requirements, such as whether there was a “real possibility” that the employers would take such a step, or whether it would have been “feasible”.

Having had this preliminary issue determined in their favour (after over six years of litigation) the way is now open for the women to proceed with their substantive claim, which involves establishing that their work is of “equal value” to that of their comparators. This case sends a clear signal to the lower courts that they should keep the preliminary issues on comparators and substantive issues separate. The Supreme Court also pointed out that, looking at decisions from the European Court of Justice, it could find no case where the principle of equal pay has not applied between men and women who work for the same employer.

Given the expense of equal value claims, employers will continue to take preliminary points. The lesson from this case is that employers will find it difficult to use a multiplicity of establishments to knock out equal pay claims at the outset. Local conditions may however still be highly relevant in establishing a material factor defence.