I approached my manager this evening for a conversation to clarify the situation after he had informed me that I am not allowed to do overtime for him for the rest of this week as I have had 2 days off sick at the beginning of the week. I rang my manager this afternoon to advise him I wanted to return to work even though I still wasnt at 100% full strength and he said that was fine, to go ahead and come in as there was always plenty of light work to be getting on with, to do what I could and he would see me later that today. No actual time for me coming back in to work was specified during this conversation, nor was the fact that I could do no overtime for the remainder of the week. I regularly do overtime on a daily basis flexing my hours up to 39 per week to help myself bump my wages up and to help the company as we have a large workload at the minute. I clocked in at 7.41 this evening and had my return to work meeting which was brief and went ok up until the point my newly appointed manager realised I had a long spell of absence last year due to personal circumstances, his attitude towards me from that point became quite cold and aloof. He advised me that I should be on light duties for 48 hours as I had admitted myself I was still not feeling 100% strong and my job is very physically demanding. I agreed with what he said about light duties (not being allowed to do overtime was not mentioned during the meeting at all) and we both signed the return to work statement. I was then allowed to go to the shop floor and start work at 8:10pm. It was never mentioned at the meeting or during the phone call that I would not be allowed to do overtime or that there would be any implications from my agreeing to do light duties and if I had been made aware of the implications during my meeting I would of questioned it in my return to work meeting before signing the return to work document. It wasnt until 11.55pm when I asked him myself if I was still ok to start at 4pm the following day as I usually do (my shift is 9pm-1am and I usually work from 4pm to 8pm as overtime). The conversation that followed took me completely by surprise and left me feeling extremely uncomfortable and upset as up until today he had always appeared happy with my performance at work and keen for me to do any overtime I was able to. It was only at this point that he mentioned I would not be able to do overtime for the rest of that week due to the phased return to work. He then pointed out that he had been laughed at by the other managers for trying to help me progress within the company when he was unaware of my absence record and that I had basically made him look foolish for him being unaware of this when I stood no chance of progression. This is not something I did intentionally and I had assumed he, as my manager, was aware of my history and record within the company. Up until today he had been pushing me and helping me work towards becoming a supervisor within the department. Doing overtime is the norm on my department as we are all on 20 hours or less contracts and the company relies on us flexing up our hours as necessary and in return we rely on the overtime to bump up our part time salary. The overtime is offered to everyone and there are some (including myself) who are consistent and regularly do the extra hours. There are still numerous people doing overtime on my department including a new starter who has only been with the company for 2 weeks. I went and spoke to my supervisor at this point as I didn't know what else to do and he advised me to go back and talk to my manager again raising the fact that I had been allowed to start early today. I told my supervisor that I would like him to be there for the conversation but as we are very short staffed at the minute said that I understood he didn't have the time so went back and spoke to my manager alone. My manager advised me that he had spoken to HR on the previous day and that they confirmed no employee ever does overtime within the week of them returning after being off sick, I pointed out that this was untrue as I myself had done overtime during the week I returned after having an operation earlier this year. (I have the evidence to back this up.) I made him aware that I felt this was unfair treatment and may even be discrimination against me as I was being penalised for admitting to feeling slightly weaker than usual. The overtime is offered to every employee and my colleagues are still doing overtime within the department. I pointed out that hed said himself there was still plenty I could be getting on with. He then threatened to raise a grievance against me for me accusing him of being discriminatory and when I questioned this, and the fact that I had already been allowed to do overtime as I had clocked on 1h 20m before my official start time, I was then told that there was a chance I would now also be put on an improvement programme because he now sees me as trouble because of my attitude during this conversation. I asked him to clarify and he said that I was being disruptive and that this conversation was not helpful to the shift. He said that he thought I had just decided to come into work early out of the goodness of my heart and that I could have the extra time back in lieu. I then questioned that if I was not allowed to do ANY overtime then I should not have been allowed to start early whether it be voluntary, lieu time or paid. He then again accused me of being disruptive and said that he definitely saw me as trouble and that I would no longer be allowed to do overtime for him at all, Im the manager and I can give or stop overtime to who I please was how he worded it. . I replied that I thought this was extremely unfair and that I would be calling ACAS the next day to seek advice. His answer to that was that ACAS meant absolutely nothing to him and to do as I liked. I found my managers demeanour to be quite aggressive by this stage and he made it quite obvious he was not open to discuss this with me any further leaving me extremely upset and frustrated and just walking off at that point without saying anything else. I had a brief conversation with my supervisor about this and asked if he agreed with what my manager had said, he said no, not at all, but he then also said there was nothing he could do as he had to be seen to be taking his bosss side and was stuck in the middle. My supervisor apologised as I left the building. I left work at 12.41am very upset, taking 20 minutes of the extra I had done that day to make up my hours to 1am. I will be ringing ACAS for advice but was just wondering f anyone had any thoughts on this matter. I now know after doing some research that it is probably not discrimination as there is nothing that falls within the"protected characteristics" It definitely feels like unfair treatment though. Oh..and thank you so much if you persevered with my essay to the end. Any advice or guidance on how to deal with this would be much appreciated.