By ITV Wales Head of Politics Nick Powell
Carwyn Jones has opened up about how the death of Carl Sargeant dominated his final year as First Minister for Wales in a newly published memoir.
The former Welsh Labour leader wrote that "not a day went by when [he] didn't think of him and all that had happened".
The suicide of the former cabinet minister, days after he was sacked, is the event most widely remembered from Mr Jones' time at the top of Welsh Government - and he told ITV News he doesn't attempt to deny that legacy.
He remains adamant that he "did the right thing" when he dismissed his colleague after receiving allegations of inappropriate behaviour towards women.
Mr Jones reveals his own severe depression as "the cumulative effect of the public unfolding of Carl's story on [him] personally".
In an interview with ITV News, he said: "You can't ignore complaints when they are put before you, especially when they are in written form, and there has to be a process to deal with that.
"You wouldn't be human if you weren't affected by it, and I was affected by it.
"There was no way I could say that publicly because it would have looked like I was trying to deflect attention from a grieving family and I was not prepared to do that."
Although he recognises that this "very dark chapter in Welsh politics" has been worst for Carl Sargeant's family, he also states that his biggest fear is that it has created an atmosphere in which women won't come forward with similar complaints.
"Perhaps not even a fear, but a certainty", he adds.
The former First Minister continues to insist that his decision to stand down in 2018 had been taken after a family holiday the year before, prior to Carl Sargeant's death, but he admits that it had "more than consolidated the decision [he] had taken previously".
Video report by ITV Wales Political Correspondent Owain Phillips
Mr Jones became First Minister in 2009, after securing a comfortable victory in the Welsh Labour leadership contest triggered by Rhodri Morgan's retirement.
Carl Sargeant had organised his campaign in north Wales and his campaign manager was Leighton Andrews, who Mr Jones said "wouldn't exactly be on [his] Christmas card list these days".
That's a personal division following Carl Sargeant's death. Their relationship had survived the ups and downs of government, even when the First Minister sacked his ally, only to later bring him back into cabinet.
As First Minister, Mr Jones led the successful 2011 referendum campaign to secure the law-making powers that would transform the Senedd from the National Assembly to the Welsh Parliament.
He credits the then Prime Minister, David Cameron, with permitting the referendum when there had been doubts in the previous Labour UK government about whether the time was right.
That referendum victory came 12 years after the Assembly had first met with very limited powers, although within a year it had used its greatest power - its right to dismiss the First Secretary, Alun Michael.
Mr Jones is one of the few politicians still serving in Cardiff Bay who survive from that time, which he describes as "[his] first real introduction to the manoeuvrings and shifting sands of politics".
He said he never really fitted in to this kind of politicking and makes no mention of plotting in a pub with Rhodri Morgan, who revealed such an episode in his own memoirs.
Mr Jones told ITV News he believes the UK needs a "fundamental constitutional change".
"The system we have in the UK where effectively all power rests, in theory, in Westminster, that has to change," he said.
"We have to look at a system where this is a partnership of four equal nations who pool their sovereignty in areas like defence and border security, because that's the sensible thing to do.
"Is it that radical? Well no, it's the same model as is adopted in Canada. If it's good enough for Canada, I can't see why it doesn't work here."
Not Just Politics is a book that provides an insight into the man who led Wales for nine years. In his memoir there are moments of searing honesty, about his depression, about his adopted daughter's difficult teenage years, about nearly losing his wife to cancer.
Mr Jones will leave the Senedd in next year, which he said felt "strange".
"Within a few hours of announcing I was leaving the job as First Minister, there was a weight lifted off my shoulders.
"Don't get me wrong, I'd do it all over again. It's what I wanted to do, it's a huge honour to do it, and I'm not saying I wish I hadn't done it.
"I've been here for 22 years, but you have to move on.
"For me there are other things to do now, other things I'm involved in, I'm still very busy. But I was one of the originals here and I will miss the place."