If you have nothing to hide then telling your partner shouldn't be an issue.

Yes and yes. If it's platonic now, then there is nothing to hide.

Yes. I think it's important to be as open and honest as possible to have a good relationship

Best to be upfront with the SO.

Yes and yes. We're partners not owners. That implies both honesty and freedom.

Yes and yes. My ex was best 'man' at my wedding.

The problem would be a lack of honesty which reveals a lack of trust.

They always going to find out... always.

I would tell. I would expect them to tell. Just because that is being transparent. Yes, my partner is free to have all the truly platonic friendships desired.

It's Plato, not Pluto -- Platonic, not Plutonic.

In theory if the relationship is truly platonic then it should be fine. In practice natural selection has wired us with jealousy and it's a big problem in relationships.

Even taking it out of the realm of "former sexual partner" it is often problematic. I'm an independent contractor and for a long time now I have had a subcontractor under me. This need arose about the time my wife and I moved in together. She said, just to be up front, that she'd have a problem if my subcontractor was a woman. She was sheepish about it, mentally okay with it, but knew this would trigger jealousy, particularly if the woman were my age or younger and reasonably presentable. So I've never gone there. It's been a moot point because only men have presented themselves as candidates. But even if she hadn't said anything, I would have been very reluctant to take the risk of my wife wondering what was really going on when I occasionally met this person for lunch and spent 2 or 3 hours with them (mostly we work remotely and independently on the Internet, it is mostly not collaborative work).

Also, to be honest, I really wouldn't want the potential for a female subcontractor to misread my intentions or for her husband to be suspicious or jealous either. There's something to be said for simplicity in relationships. I hate cross-currents and undertows.

Should this even be a problem? I suppose not. But people aren't perfect, they have insecurities. And there are some hills I just don't want to die on.

As long as that ex is also crystal clear the relationship is totally platonic and isn't trying to get back with the person in question, there is no reason to worry about it either way. Telling a current SO about it depends on if that SO is a jealous or insecure person, and if it would hurt that SO more for knowing now or finding out later and concerned about why they were not told up front.

I am currently in a platonic relationship with my ex. We share children together and it is much easier for EVERYONE that we are friendly and not at each other's throats all the time. We are good friends now and get along better than when we were together. If and (hopefully) when someone new comes along, I would be completely open about it.

I'm not sure if a person should have an active platonic relationship with a former love if that person is in a present relationship. Just too much baggage and issues that could come up. Even if you trusted your present love knowing that he/she is faithful to you and not the former love, I still think you're cruising for trouble. I think I'd stay away from that potential sh*tstorm and not continue it.

Of course your significant other should know. Why not? Why lie? ????????????

Total honesty is what I like best, and absolutely it should continue, platonic or not. Whatever they want. Lol. ?

If their are still feelings on either side that can be bad for the new relationship. Sometime people just realize they are better off as friends. If that is the case no need to break off the friendship and open communication with the new partner should happen. If one or the other has feelings, then that is a different story.

It ain't easy, but it can work.

I am in that situation right now. My current girlfriend has a problem with my friendship with my exs. These are STRICTLY PLATONIC but her own insecurity is making the situation hard. I will not disown my friends for such a needless reason.

One would hope that honesty is the best policy in relationships and therefore there is no reason not to tell your sgnificant other about a platonic relationship with a former partner.

If there's nothing to hide there's nothing to hide.
I believe in being completely honest about everything.

I think there should be honesty, so yes, they should tell their significant other. I think there should be room in a relationship for friends of any gender.