Only a year ago Labour’s deputy leader was stricken at his party’s dysfunctional disarray. Now he’s making parallels to Blair’s 1997 landslide and is convinced the Tories are on the brink of collapse. But will his bitter row with Unite’s Len McCluskey ever be resolved?

The first time we met, in 2014, Tom Watson was essentially operating a one-man child abuse hotline out of his parliamentary office. His reputation as a champion of phone-hacking victims made him one of the few politicians alleged victims would trust with their stories, and Watson found enough of them credible to take claims of a VIP Westminster paedophile ring very seriously. “There is no doubt in my mind,” he told me, “that at least one politician abused kids.”

When we met again, in the summer last year, Labour was in dysfunctional disarray, reeling from the aborted coup against Jeremy Corbyn. Watson was barely even on speaking terms with his leader, and looked stricken. He said that entryist “old Trots” were infiltrating Momentum to hijack control of the party, which got him into hot water with Corbynistas. He didn’t seem to mind upsetting them, though, which made me think he assumed they’d soon be finished off by inevitable electoral defeat anyway.

When we meet again this week, the Westminster VIP paedophile ring no longer looks to most people like a plausible scandal. Allegations of rape against the late Sir Leon Brittan, which Watson helped publicise, have been investigated and found baseless – and Corbyn has defied his deputy’s predictions to lead Labour to the brink of power. So I expected to find Watson somewhat chastened, eating if not humble pie then at least his words.

For that matter, he might be in the mood to eat anything, having gone on “hunger strike” this week in solidarity with two Guantánamo Bay prisoners who are refusing to eat in protest at their incarceration. Horrified to discover that Donald Trump had scrapped America’s longstanding policy of force-feeding captives on hunger strike, Watson undertook a 30-hour fast to draw public attention to their grisly fate.

Facebook Twitter Pinterest Jeremy Corbyn, Watson and other MPs at this year’s Labour conference. Photograph: Pete Summers/REX/Shutterstock

But the figure who greets me in his Westminster office looks almost indecently cheerful. I have never seen Watson this happy. Then again, I’ve never seen him second-in-command of a party he believes to be just inches from power.

“Theresa May doesn’t even look as if she wants to lead. You can support a weak leader – but a leader who doesn’t provide any leadership just leaves them in stasis. There’s no leadership at all. They don’t have a plan, they don’t have a narrative, and at any point they could unravel. I’ve never seen anything like it. These are unprecedented times. I was right in the middle of the Blair/Brown years, but this triangle at the core of government – Hammond, May, Johnson – none of them can get on. It’s so unstable now that we have to be ready for them to collapse at any moment.”

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Labour, on the other hand, are “buoyant”. This week’s PMQs was: “The best I’ve ever been to. Jeremy was fantastic and I could feel our backbenchers solidly behind him. It was great today.” Given the choice, he’d like another election called as early as possible, but suspects May will limp on until Brexit talks are concluded. Then will Labour win? “Look, even in 1997 we knew better than to say that.” It is the first time I’ve heard anyone in Labour draw a parallel between Blair’s first landslide and the party’s prospects today.

Watson doesn’t buy the idea that the Brexit talks are failing because the referendum result is impossible to implement. “No, I think it’s achievable. I just think they haven’t got a settled view around the top table on what their plan should be. They’ve still got people who think that crashing out of the EU is a realistic and, some even think, a positive option.” Does he hear anyone in his own party argue for no deal? “No.” Watson shares Amber Rudd’s view – no deal would be “unthinkable”.

While in favour of maintaining single-market membership during a period of transition, he wants to make it very clear that contrary to recent press reports, permanent membership is not his preferred model. Only in the unlikely event that the EU revised the free movement of people as a condition of membership would Watson reconsider. He won’t rule out a second referendum, but even if we fail to agree a deal and face crashing out of the EU, he thinks another vote is still “highly unlikely”.

Facebook Twitter Pinterest Watson leaving a meeting in March at Unison’s headquarters in London as he and Corbyn issued a joint statement agreeing to strengthen party unity. Photograph: Stefan Rousseau/PA

Watson talks about Brexit with studied caution; he is a remainer whose West Bromwich East constituency voted by 70% to leave. He would still vote to remain again, though, and says Corbyn would, too. The pair now talk “every day”, so I ask him what changed – Corybn’s leadership, or Watson’s mind? “If you’re asking, are we getting on better, yes we are. A lot better.”

I ask about relations with Momentum. Having praised the movement in his party conference speech, does he owe its supporters an apology? He sighs. “Listen, what I said last year was that the vast majority of Momentum members are very bright young people who want a more fair and equal society. Everyone forgets that. But I also think it’s slightly ironic that since then Momentum has had to expel some of those Trotskyists from its own organisation. So I’m allowed a wry smile on that.”

Was he worried about verbal abuse from Momentum members at the conference last month? “No, not at all. But I was a little worried about grief from Len McCluskey.”

The Labour deputy and Unite leader used to be close friends, once even flatmates, until Watson’s public criticism of Corbyn last year unleashed a Shakespearean feud. The two haven’t spoken a word to each other since, and when invited to the same event pointedly ignore one another.

Watson built his political career in part at least on his reputation as something of a bruiser, and any mention of his name within Labour circles usually elicits knowing smiles reserved for the kind of men you wouldn’t want to mess with, but like to have on your side.

Watson always pretends to be mystified by his reputation. In my experience, however, such reputations seldom appear out of thin air, so it is a surprise when he tells me he finds the feud with his old friend nerve-racking. “He’s a very powerful man, you know, who’s not very keen on me. It’s slightly disconcerting and, on a personal level, it’s quite sad and a bit frightening,” he says.

Facebook Twitter Pinterest Watson says he would vote to remain again if there was another referendum, although he believes that’s ‘highly unlikely’. Photograph: Hannah McKay/PA

Frightening? “Well, you know. A bit intimidating. You listen to radio interviews with the general secretary of Unite calling me a back-stabbing neoliberal – it’s not pleasant, is it? But you get on with it.”

Has Watson ever considered picking up the phone to offer a truce and make peace? “No. Because it’s a personal relationship that is irreconcilable. On a political level we’ll manage the relationship fine, and that’s that.”

The mind boggles to think of the secrets the two must have on each other, but the nuclear arms principle of mutually assured destruction will probably ensure we never know. According to Watson, however, McCluskey is busy doing his best to make him lose his job. The party is considering an idea to appoint a female second deputy leader, but when I ask Watson what he thinks, he replies: “Well, obviously some of it is personally targeted, so it’s a bit uncomfortable.” The gender-equality argument is nothing but a spurious disguise, he says, for a vendetta against him.

Facebook Twitter Pinterest Corbyn and Watson at party conference in 2016 after an aborted coup in the party against its leader. Photograph: Oli Scarff/AFP/Getty Images

Watson does think the next Labour leader must be a woman, and can conceive of no circumstances in which he would support a male candidate running against a woman. “That is a long way off,” he adds hastily, taking care to make clear for the third time in an hour that Corbyn’s leadership is now unassailable.

If politics is, as people say, showbusiness for ugly people, it strikes me that the power dynamics in Hollywood that allowed Harvey Weinstein to get away with decades of abuse must also apply to Westminster. The Houses of Parliament are full of young women whose political ambitions must be easy to exploit by older, powerful politicians, so I’m curious to know if Watson hears the same sort of rumours that used to circulate about Weinstein.

“I don’t know of any.” Really? “No, no.” I’m amazed, but Watson is adamant. “Well,” he adds, “abuse of power I’ve obviously raised with the child abuse stuff.”

If Watson has the slightest concern that he may have been overly credulous about allegations of establishment abuse, it doesn’t show. No, he says calmly, he doesn’t think he was too hasty, nor made any claims he would now retract. “I think I did the job of a backbench MP. I shook the tree. I know people think I said too many things publicly, but there is a lot more privately that Alexis Jay will have to look at with her team.” Does he expect Jay’s inquiry to vindicate his suspicions? “Only time will tell.” Its inquiries into historical abuse in Lambeth, he adds, “could be quite significant, and cast more light on the goings-on around Westminster as well”.

As a well-known and powerful politician himself, single since he separated from his wife a few years ago, I wonder whether he feels he must always be careful to keep his professional status out of his private life.

“Look, I’ve got enough on my plate. If there are any 50-year-old divorcees out there who want to put up with a political obsessive, they can send me an email. But I’m not particularly interested. Being deputy leader of the Labour party has many complications, but when it comes to my private life, I try not to play the power card.

“I actually don’t consider myself that powerful. I know some people might perceive me as that, and that’s the point you’re making. But at the end of the day, I’m a working-class kid from Kidderminster who happens to be deputy leader of the Labour party. Who knows for how long. I suppose that’s down to Len McCluskey.”