To inform a colleague her partner is on a dating site

[DizzyDalek]

So colleague isn't someone I see on a daily basis,she works in a different department,I don't know her that well but I know people who do know her better than I do. I found her long term partner on a dating site,he is looking for fun dates and nothing serious! They haven't split up,as far as she is concerned everything is good. They have a baby together and he is step -dad to her other children. I know I would want to know if my partner was doing that and if it was a good friend of mine I would tell them.

Also, there are no questions to ask or answer. He has a dating profile. Once she knows that, she knows everything the OP knows.

Does it definitely show the profile is recent? I was with my current partner for ages when my friend admitted he'd come up as a match with her. But he hadn't logged into his account for months but because he hadn't removed it, it still showed to potential matches.

I'd want to know, and i'd prefer to be told by email/text/letter than face to face.
Face to face i wouldn't be able to hide my initial emotional reaction and it's something i wouldn't want anyone, whether friend or relative stranger, to see.
I'd want time to properly register what i'm seeing/reading, and compose myself to then see people face to face.
Yes to the not gossiping around the office, and reassuring that you haven't and won't be telling anyone.

One niggle though, it annoys me posters saying "All women should be told if her partner is cheating", no, every PERSON, regardless of gender, deserves to be told their partner is cheating.

Actually, OP, are you even sure the profile is that of this distant colleague's partner? A lot of dating sites use aliases/usernames and, in some cases, random pictures nicked from anywhere online. Given that you don't know this woman very well, how come you believe it's her partner? How many times have you met him?

Given that many more people are now rejecting the idea of compulsory monogamy anyway, meddlers really do need to take a good look at themselves before getting involved in the relationship issues of people they barely know.

I would want to know,however in your shoes I would be reluctant to get involved. I think the prospect of a shitstorm at work would prevent me from saying anything tbh