What do I tell my son?

[LeoLibra18]

I separated from my ex very recently, we'd been pulling apart for months actually.... Our relationship was very turbulent. There was at the start, Infidelity from his part, and from then on, constant breaches of trust, lies, crossed boundaries and so on. But boy, when it was good.... It was the best.
I had a lot of love for this man so I accepted this behaviour for around 2 and a half years. I introduced him to my son quite quickly into our relationship because I fell head over heels. I honestly believed he was the one. Him and my son have had a great bond the entire time. My son idolises him. But I had to make the choice, there was no way I could allow myself to be suffocated by this situation any more.
Do I brush it off every time my son asks for him or asks about him? - which is what I've done in the past during periods of fall outs... Probably knowing that we'll end up right back together.
Or do I sit him down and have an honest conversation with him about it?
My son is 7. I feel like speaking to him about it will solidify the situation. But I know he's going to be so sad. My heart breaks for me and my son.

I think sit down and talk to him about it.
Say that he wasn't making you happy anymore. Your son will probably suspect something is up anyway.
Don't to the make up break up thing with the guy

You just need to tell him honestly that you and partner have decided to go your separate ways and that you both won't be seeing him any more. He doesn't need to know the reasons or the ins and outs of the relationship. And please don't introduce a new partner to your son too quickly again. It's unfair to let him get attached to someone who may not be sticking around.

Are you definitely done with him?

If you're sure, just two your son you won't be seeing him anymore.

Your son deserves to know that this man isn’t going to be in his life anymore. Fobbing him off isn’t fair.

I feel like speaking to him about it will solidify the situation.

It sounds like you don't want to tell your son that he won't be seeing this man again as you are no longer friends (which is the simple explanation you give to him) because you still think you may get back together. You sound very enmeshed with him and - honestly - with the drama of big love.

He is a cheat. there is no big love here. Your son doesn't idolise him. He was put in a position at the age of - what - 4 or 5 - where his mum clearly wanted him to like this man a lot - so he did. you shouldn't have allowed any bond to occur with your son and this random cheater.

Sorry OP I don't mean to be mean to you but your post says to me that you are still wanting this man in your life and are using your son "idolising" him to justify it. Just break it off and forget him.

Thank you all, some were more brutal than others but I feel as though you are all right. I will speak with my son soon and let him know. It's all a bit fresh right now so I will speak to him in the next couple of days.
Someone mentioned that I shouldn't have encouraged a bond between my son and a cheater and isn't hindsight a wonderful thing. I was fed with an unreal amount of promising words. Talk of marriage and children and holidays and blah blah blah.... I had a serious case of rose tinted glasses.

Your son deserves to know he's gone, and this relationship needs to stay dead.

Whatever he promised you, his actions screamed otherwise. If you have him back, you may as well just print 'doormat' on your forehead as he'll know he has permission to walk all over you. And that'll be a terrible environment for your son.