My male maternity cover was given my job at an inflated salary

Whilst on my second maternity leave I was not informed about a post that had arisen with my small team of three. The post that was advertised was essentially my job role, at a far higher pay grade. The post was given to the man covering my maternity leave. It was devastating that a person covering my role for less than 8 months, (a role that I had held for many years) was promoted to this senior position, he was only able to get the specific knowledge and experience for the post by covering my position whilst I was on maternity leave. The organisation agreed my grievance was justified and ‘promoted’ me to a level below the one being held by my maternity cover. I remain in place, doing menial admin tasks, in a post that in no way resembles my original job.