Two colleagues are carrying on and affair and it's really unpleasant for everyone else in the department

focus on but the behaviour that affects the ability of other employees to do their jobs effectively and in a non toxic environment.

And also mention damage to the company's reputation. If visitors are noticing and commenting, they will go away and talk about it.

@CurdinHenry

This is obviously unacceptable behaviour and needs to stop. I'm not an HR person but was a TU rep for many years.
I think the correct way to go about this is via HR.
The affair in itself is none of your business, but disruptive behaviour in the office is. Raising a grievance puts you in the middle, where you shouldn't and really don't need to be, and puts responsibility on you. Far better a complaint to HR, preferably co signed by other staff.

The right thing to do is report it through the correct channels. However, not all companies follow the right procedure and you may loose your job if this head of department dude is tighter with the company than you.

Personally I would not speak to or email him. Never write anything down that could be used against you.

I would either let HR know anonymously or I woud tip off the wife and let them deal with it.

As much as we like to put faith in the companies we work for - they don't always do the right thing (probably because they are usually run by men).

the quickest way to resolve this is to just tell the wife.

Yeah, you are right OP.
Raise a grievance, it would be better if your colleagues will do the same as the situation you are all working in is becoming draining.

I've been in almost exactly this situation, that went on for about 4 or 5 years and also included the very bitter and expensive divorce of the person in the more powerful employment position in the background. The workplace jealousy and the volatility were features of those years too.

One colleague did raise a grievance, not just on the grounds of the relationship. In reality, everybody there got some dents and bruises from that, it was really unpleasant for everyone but especially the 3 main people at the centre of the grievance. The person who raised it also lost their job, as well as the person who, in their eyes, was the villain in the tale. The major changes and factions sped up heavy-touch restructuring from above beautifully, too. Having seen how this went, I would think more than twice if there was a case that may have meant raising a grievance again.

You may have more success with a small group, a party line on the effect on the work, and a quiet word, not gathering armour and popcorn.

That’s going to happen anyway! OP may as well watch it unfold rather than be involved with it unfolding.

HR probably already know about it. I had something similar at work very many years ago. It was the talk of a big firm. I was warned to stay clear of it by my manager a couple of days after joining. I’d leave it be, they will burn themselves out.

Yes, fuck the poor wife’s inevitable heartbreak, let’s all get the popcorn out and watch with glee whilst her life implodes 😳

How embarrassing for them. YANBU. I would have a word with HR.

They are shockingly unprofessional and should be ashamed. I feel for the woman actually, she is obviously going through emotional turmoil, affairs can do that to people but goodness, have a bit of shame.
If so many people are aware of the affair i’m sure it will come out sooner or later.

How do they think they're keeping it secret if she acts like a bunny boiler when he engages with other colleagues??

Go to HR. Try to keep it factual. You don't want a witch hunt but several people reporting might add weight, particularly the person between them in the chain of command.

Is this a small or big firm? Do you have a code of conduct? If it’s explicitly against company code report to HR immediately

Definitely do not approach either of them. That would be a very bad idea which could rebound on you. Keep it formal and official by speaking to HR or overall boss. Make sure that it’s not the affair that you focus on but the behaviour that affects the ability of other employees to do their jobs effectively and in a non toxic environment. Go armed with approximate dates and incidences of such behaviour.

Definitely report it, but keep it professionally neutral reporting the behaviours but not the affair. Anyone with a brain would read between the lines, report her behaviour which happens when a female member of staff speaks to him and how that impacts on peoples roles and ability to do their job, the toxic atmosphere, how there have been questionable decisions made by your head of dept such as x, y, z etc.

and then check their dairies to see when hr have meeting with them, hopefully in a room with glass doors and work out a place where you can hover and hear but not be seen x

Or drop her a hint that he’s getting quite close either to someone in hr or someone who manages him……and watch the problem solve itself……

If it's against policy the one who is the boss will be sacked.

YABU in that you are only "thinking" of raising a grievance and not just doing it.
They are bringing their private lives into work and having stand up arguments in the office, acting out their own little soap opera with you lot as their unwilling audience.
You've said it makes you uncomfortable and not wanting to come to work.
Why haven't you done something before now?

Keep very detailed notes.
Specifically the volatility of the situation, unprofessional nature, visitors commenting.

Lean into it from an angle of feeling "unsafe in your working environment" that the unpredictability of the volatility of their interactions.
That you are now very nervous and stressed about going to work, that you have increasing anxiety connected to your work environment.

Make it a safeguarding issue in the work environment.

Their private lives being played out in the office is making YOUR working environment unsafe.

Keep very detailed notes.
These always add weight to a grievance.

Is there a whistleblowing hotline?

Oh my god stay out of it as much as you can and keep your head down.

definitely don’t go to HR and say they are having an affair. The only thing you can really do is raise issues with your line manager that are affecting you, eg screaming matches in the office or one of them telling you not to talk to the other. Don’t even MENTION the word affair or that you think they’re sleeping together.

Fgs 🙄I'm more in the "You stupid cow" camp.

I can’t understand people like this . How utterly selfish not to mention unprofessional. As this is having a direct effect on the department I would report. Why should everyone have to put up with this drama ? It’s a form of bullying if colleagues are afraid to speak with the head of department