I had been demoted without being told let alone consulted

I was a senior manager at an NGO working 3 days (agreed reduction from full time after 1st baby).  To clarify, there has never been a question of competency – I have always done what is required and more. Before going on maternity leave with my 2nd baby I was informed a restructure may be happening.  Once on maternity leave, I heard nothing more for 5 months until someone on my team asked to visit me at home – she showed me a copy of a presentation given by the CEO about the restructure at a full staff meeting (which I hadn’t been invited to).  The presentation included a new organisational structure diagram with my initials against a more junior role beneath (and reporting to) my maternity cover (a man, also part time) who was marked down in essentially my (old) role just renamed.  I had been demoted without being told let alone consulted.  I requested a meeting with the CEO at which he told me that all the senior manager roles had now been made full time and so unless I would go back full time then I had to accept the more junior role.  After I expressed concern about how this was all being dealt with, he then put a redundancy option on the table.  Not wanting to go back full time or take redundancy, I accepted the more junior role on the same pay.  On my return to work 4 months later I was astonished to find that I was indeed reporting to the man who had been my maternity cover (he had been asked to stay on) in essentially my old role (though renamed) and that he was still doing that part time.  In other words, I’d been demoted on the basis that I wouldn’t do the job full time and yet my maternity cover was allowed to do just that.  I raised the issue with the CEO stating that it was unacceptable, and he did then sort it with a reshuffle so my maternity cover is now on my level and we’re both reporting to the full time (currently vacant) position.  The overall result is, however, that I am now more junior (with no say in the key decisions of the organisation) as compared to male counterparts who I used to manage or at least be on the same level as.  I have no doubt that my career has been penalised for taking maternity leave and opting to go part time, albeit that this probably hasn’t been done maliciously.