No, salary protection does not count as a valid reason in equal pay claims. You simply need a comparator doing equal work for more pay.
I have known lots of people trying to make the case that employees who have been at company longer shouldnt have better terms or pay.
Unfortunately, all were advised they didnt have a case. The 2 who pursued it lost
Because the companies can prove both were employed at standard rates for the industry at the time they were employed. And both have had increased pay in line with industry norms.
Unless you can prove sex is the factor that decided the payment terms, its not sex discrimination.
Here we have.
The man was employed when wages were considerably higher
He has worked for them for longer, which often counts for something. In lots if companies, people get more holidays for long service.
He negotiated to reduce his responsibility but maintain his wage. The employer may have had very good reasons for this, that have nothing to do with sex.
Companies can employ people on different contracts. They cant if it based on sex. But they can, because the industry pays less now than it did back then.
The OP would need to prove the decision to keep himno his wage is based on him being a man. Not based on him being a long standing employee.
If it was simply equal pay for equal work, then most companies that now pay less than they did 20 years ago would all be breaking employment law. But they arent.
The back ground is relevant.