Alastair Campbell: We nearly split over Iraq but Brexit has brought us together

But secret body language isn’t really necessary because Campbell and Millar are so frank. I feel like a marriage guidance counsellor.

“Do you know Alastair’s least favourite word in the entire English language?” Millar asks. “Contented. I am contented. The thing he hates.”

“You are not fully contented,” he says.

“Well it’s quite hard to be living with you.”

For instance Millar likes box sets. Campbell: “I hate box sets. People who gorge on box sets are retired from life. Waste of time.”

When I ask if they like to potter around on holiday she says “yes”. He says, “no”. If they wake up on a peaceful Sunday, says Millar: “The comments within five minutes will be, ‘What are we doing with our lives?’, ‘I don’t feel relevant’.”

She dreams of dog walks and holidays; he is terrified, he says, “of being bored”. This restlessness must be exhausting. Can’t he find inner calm? “He went to yoga once,” she sighs. “I’m not taking him again.”

Meanwhile Campbell is publishing volume six of his diaries, which charts the period 2005-2007 when Tony Blair handed the baton of New Labour power to Gordon Brown (at least two more volumes are to come, making them, arguably, a literary box set).

Campbell records, alongside the intense pressures of advising the two warring leaders, the growing crisis at home: the constant rows with Millar over the Iraq war (which she opposed) and his job, which she asked him to leave in 2003 for “a new life” with the family.

He quit. But very quickly was “sucked back in”. “Well, I would say [Blair and Brown] were pulling me in,” he says. “Fiona would say I was willingly going back.”

“Who is more important, Tony Blair or me?” was her constant refrain.

Their marital crisis peaked in 2006 when Campbell blew during a row on Hampstead Heath and began punching himself in the face. Millar was terrified. She’d nursed him through his first terrible breakdown in 1986 (afterwards he also went into recovery for alcoholism) and saw that he was again “suffering from a psychotic breakdown and depression” because of high stress and no professional help.

They found a psychiatrist, David Sturgeon, who prescribed anti-depressants. “He persuaded me that there is nothing wrong with pills,” says Campbell. “In the past I’d tried to get off medication as soon as I could.”

Now he has been on Sertraline for three years. It works. Despite “unpleasant” side-effects, like “occasional” loss of libido, “I’ve been lucky. And listen, cost-benefit analysis: definitely positive.”

They are talking so openly about their 38-year relationship today to raise awareness of mental health issues. Campbell, 60, wants the Government to act urgently to ensure sufferers get fast local access to psychiatric treatment. Millar, 59, wants partners recognised. “Being the partner of someone who is mentally ill is really tough,” she says. “Often they suffer but nobody talks about them. You blame yourself. Some people with mental illness can be manipulative and make you feel it’s your fault. It can be quite abusive. I am quite strong, well-grounded. But a different person mightn’t have coped.”

Campbell admits he took things out on her. “Not in a deliberate way, just that she would be the person that I felt I could. I didn’t have to pretend.”

He describes returning from work with Blair so exhausted that he’d slump on the sofa and refuse to speak. This “catatonic” state could last a whole weekend, with Millar asking “what’s wrong” to no avail. “Fiona would take that personally,” he says. “She’d switch on the telly and I’d be with Tony having a laugh. She’d say, ‘You’re here and you’re bloody horrible. At work you’re all smiley smiley’. But when I was depressed it was hard to function.”

Sturgeon persuaded Campbell look at things from her point of view. “Finally someone allowed me to be listened to,” she says, “without it being turned into, ‘If only you supported me more it would be different’.”

Campbell adds: “I felt anger when she put up barriers. What he helped me to understand was that the barriers were her self-protection.”

Sturgeon compared Campbell’s relationship with Blair to having “another woman” and his job to an addiction. “It was like a kind of cross addiction really,” explains Millar. “He was addicted to the adrenaline — to the ‘demon’ as David called it. The demon inside you that keeps drawing you back but is ultimately quite damaging.”

Of course Millar had worked at No 10 too, as Cherie Blair’s adviser between 1995 and 2003. She fell out with Blair over Iraq and wanted to resign but because Campbell feared how it would look “publicly” was pressured to stay.

“And I regretted that,” she says. “I felt very angry.” Campbell doesn’t feel “bad” for persuading her to stay. “I had to compromise too.”

In the early days Downing Street was a “thrill,” but juggling crazy hours and small children (Rory, Callum and Grace) was tough.

Being “good with the kids”, says Millar, “is the easy part for dads. It’s all the other stuff: bins, laundry, clothes, school trips, blah, blah. Alastair says I’ve semi-retired now, but 30 years of being a working mother takes it out of you. I remember my mother saying, ‘There’s no such thing as women’s lib, women just do two jobs’. It’s true. It’s different to a man’s career.”

Every morning she went swimming at 5.30am, returning for the school run as Campbell was leaving. Both would work until at least 9pm before starting the whole “treadmill” again.

“We didn’t do parenting very well,” she says. “Looking back I should’ve done it differently.” How? “It probably wasn’t right to have done that job. There were easier jobs.” Millar says that the children hated them working only “when the job itself was causing conflict between us, which it was, a lot — especially over Iraq.”

Campbell says he sometimes took Saturdays off to drive the boys to Burnley for the football. “I remember Callum saying, ‘Yeah but we used to be sitting in the car and you’d be on the phone for four hours on the way up, four hours on the way back, shouting at people’.”

Indeed, it hasn’t all been “plain sailing” with the children — “One was an alcoholic,” says Campbell, “Now dry after four years, but they’ve done really well. They are amazing kids.”

A nanny plus Millar’s parents, who lived in St John’s Wood, provided support. Who cooked? “I did all the cooking Charlotte,” Campbell says. Millar makes a noise like pfffff. “He has never cooked anything in his life. He’s never even been in a supermarket.”

“I have,” he protests. “For a signing: Tesco’s Book of the Month.”

I ask if she ever thought about leaving him. “Yes. Several times. I visualised what life would be like if we separated. But in the end I thought leaving wasn’t right for the family.”

If Iraq nearly ended their relationship, Brexit has bought them back into step ideologically. Both agonise over how to stop Brexit (although only Campbell stares at the ceiling all night with anxiety and insomnia). They use “we think”, “we believe” when they discuss their views, such as there shouldn’t be a second referendum.

Actually Campbell’s worries are endless: Trump, the Labour party, which shirts to pack for a work trip, predeceasing Millar or the kids. “All that shit.” The other night he had a “horrible” dream that Trump, “came into the bathroom and told me to stop playing my bagpipes”.

I ask Campbell why he is so angry. He seems surprised. “I get very frustrated. I am volatile. But I don’t think angry,” he says.

Hilariously he argues that Theresa May’s “strange” pre-election team (who have been accused of bullying, abuse and controlling behaviour) were far worse than he ever was.

Didn’t he shout and swear? Was that different? “Absolutely,” he says. “I wasn’t angry and nasty.” This is maybe the most Malcolm Tucker thing he’s ever said.

“The thing with me is overblown,” he persists. “I’ve always thought that. You talk to, say, Robert Peston,” he falters, perhaps at the memory of calling Peston “a c***” in public. “Maybe not Robert, but other political journalists. I had tough robust arguments with them, but you wouldn’t get their wives telling you I bullied them.”

“Apart from the one you punched,” Millar interjects.

“That was when I was still a journalist!” He cries. “The other difference is that we were competent. We knew what we were doing. We were good. Theresa May’s operation has been a shambles from start to finish.”

Explosive rages mask deeper issues, but Campbell is not yet ready to explore them and resists his daughter’s efforts to get him to see a therapist. “I see a psychiatrist,” he says. “And I like seeing a psychiatrist.”

I ask if his father — a vet — was ever angry but the memories are vague. “I can’t remember him hitting me, but I imagine he did because that was the generation.” His father was “tough. From the Hebrides”.

But he hid his breakdown in the Eighties from them “because my brother Donald, who died last year, had schizophrenia. I just didn’t want to put them through it again.”

It was Millar’s parents who supported him. She says: “I remember my father saying to me, ‘You’re going to have to think really hard about whether you are going to stay with this guy’. I was scared. I thought you were going to hit me,” she says to Alastair. “You were foaming at the mouth. We’d never come across anything like that before in my family.”

Has Campbell ever hit a woman? Millar snorts: “The only domestic violence here has been the other way around.”

“I have been hit by a woman,” Campbell confirms. “But I couldn’t hit a woman, no. I think one of the reasons I was punching myself on the heath was…”

Millar interrupts, “What, so you wouldn’t punch me? No. It was self-hatred.”

“It was a turning point. Everything boiled over. I don’t think it will happen again.” Campbell continues. “I don’t know though. Who knows?”