08/06/2017 8:06 AM AEST | Updated 08/06/2017 10:57 PM AEST

Jeremy Corbyn: If I Become PM I'll Tell Trump 'You're Wrong'

The attack line, when it came, was classic Jeremy Corbyn.

At a rally in Watford on his final campaign tour of the general election, the Labour leader vowed that if he became British Prime Minister he would give the President of the United States a piece of his mind. Theresa May might want to hold Trump’s hand, but Jezza would take a stand.

“I would not be afraid to pick up the phone, or write a letter, to Donald Trump and say ‘listen mate, you’re wrong on the Paris climate change agreement!’”

Impeccably polite and unmistakeably English – writing letters, saying ‘mate’ – Corbyn’s idea of being firm with Trump prompted one of his biggest cheers at the event in the key Tory marginal in Hertfordshire.

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Donald Trump: He Who Must Be Named.

Despite the sign at Watford Junction stating ‘Alight Here For Warner Bros. Studio Tour’, there’s little American glitz or glamour about the town that’s just a bus ride away from the nearby Harry Potter experience.

But for Corbyn supporters gathered in the square, Trump was He Who Must Be Named.  The line about standing up to the President won the biggest cheer of the afternoon, not least from supporters wearing the latest on-trend Corbynista fashion item – a white T-shirt with the Nike swoosh replaced by one word, ‘Corbyn’.

“I love that he’s all about fucking Trump. He’s not just always going to go along with the US,” said student Hannah Prizeman.

“We have a reality TV star that is the President, the leader of the free world, it’s not OK. He’s chauvinistic, misogynistic, and we finally have someone that reflects the people of Britain, who’s going to fuck Trump.”

Before Corbyn can think of his own ‘Love Actually’ moment in No.10, he has of course to win seats like Watford, a seat that was Labour under Tony Blair but has had a Tory MP since 2010.

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Harold Wilson ended Tory rule with a Watford win. In 1964.

It was not Blair but another former Prime Minister that he namechecked, however, in his opener to woo the crowd.

Harold Wilson clinched Watford in 1964, to take Labour over the line and end “13 wasted years” under the Conservatives. “Labour will do it again!” Corbyn yelled, to cheers. If he wins Watford, he gets the keys to No.10.

On the fourth of his six whistlestop campaign visits on the final day (and the 88th rally of his entire campaign), the Labour leader sounded slightly hoarse but had bags of energy that belied his 68 years.

“We have grown in support, and grown in stature, and grown in confidence over these past seven weeks,” he said, a hint that he thinks that the ‘surge’ in some polls is real rather than imagined.

The ‘experts’ and commentator had written him off at the start of the campaign, he said. “It was going to be a walkover. Well, sometimes people are wrong.”

The Watford rally didn’t attract the enormous numbers of some of his other events, yet it was typical of the genre. Sly & The Family Stone’s soul classic ‘Everyday People’ as his warm up song, a truck with an ‘Abolition Of Tuition Fees’ poster as his backdrop, the now-familiar chant of ‘Jeremy Corbyn’ to the tune of ‘Seven Nation Army’ ringing out from gathered youths, they were all there.

Corbyn’s stump speech had the usual applause lines about restoring the NHS, free childcare, a “big decision to abolish college and university fees” (cue a big ‘whoop!’ from the crowd), the restoration of “hope and respect” in Government. “It’s not just about electing MPs, it’s about what we are offering this country,” he said.

After the cheers died down at the end of his speech, Corbyn shook hands, took selfies and signed autographs for the faithful. “He touched my hand!” squealed one student to a friend.

Kirsty Thorpe was typical of those who attended. After shaking her leader’s hand, she told HuffPost why she felt his message resonated. “He’s got this tour and he came to Watford, a second time in a week,” she said.

A mature student studying social care, she pointed to her West Herts College across the street: “The tuition fees thing, it’s really pertinent to Watford.

Kirsty Thorpe (right) with her friend Megan.

“But so is housing. There’s been a lot of redevelopment in Watford but there’s a housing and homelessness crisis. Our MP was a hotelier and property developer. He should never have been our MP in the first place.”

“I’ve been homeless myself, I worked and then after 20 years of paying taxes I lost my job and became homeless. I had a spinal injury, relationship breakdown, I fell foul of the private rental market. I lived in the YMCA for three years.

“I had to take a huge amount of finance to fund my study. I’m about £30,000 in debt after two years. Abolishing fees won’t help me but it doesn’t matter. I want it for future generations.

“I’ve been recruiting people hard and fast, people who weren’t even going to vote. I’ve canvassed my student colleagues, my friends.”

PA Wire/PA Images

Watford certainly shows some ambition on the part of Corbyn. It is a three-way seat where the Liberal Democrats came narrowly second and Labour third to the Tories in 2010. Once a marginal, it saw its Conservative majority increase in 2015 to a substantial 9,700.

“It’s hard but I think there’s a turn, especially with the tuition fees thing,” Kirsty said.

Shahan Choudery, an academic researcher, said Corbyn’s main obstacle to winning was the “biased” media.  “He’s a man of honesty, integrity, he means what he says. He wants justice for the country, whether you’re Tory, Lib Dem or UKIP, he speaks for everyone.”

When the crowds had dispersed, Corbyn headed to the train station (his entire tour on Wednesday was to seats just off the West Coast mainline), accompanied by his large entourage of aides and staffers. On the platform, he posed for yet more selfies, including with train maintenance workers.

Jeremy Corbyn and junior doctor Zak Vinnicombe.

And there then came an encounter with that rare beast on an eve-of-poll day of party rallies: an undecided voter.

Zak Vinnicombe should in theory be exactly the kind of person who is on the Corbyn soul train (as well as the 6.47 to Harrow and Wealdstone). A junior doctor working in Watford, worried about his pay, workload and prospects, he approached Corbyn to ask if he could persuade him how to vote.

Corbyn went through social care bed blocking of hospitals, and enquired thoughtfully about Zak’s hours and job. When the train arrived at the platform, their meeting was over and ended with yet another selfie.

Yet afterwards, Zak remained undecided, if not unconvinced. “He came across as a very genuine and honest guy. He’s doing better and has surprised a few people.” So far, so good, Corbyn supporters would think.

But then came the kicker: “I’m not going to say he swayed me to vote for Labour, though it was good to meet him.

“I voted last time for the Conservatives because I thought they would do a better job. If you’re young and you see social media, you see the echo chamber. But look at what happened with Brexit and Trump, people woke up and thought ‘how did that happen?’

“There’s probably a lot of people who are going to vote for the Conservatives, and they’re just getting on with their lives. The Conservatives could do well. I’m genuinely still 50-50.”

As Corbyn headed south of Watford, and finally to the warmer embrace of his backyard of Islington, Zak’s ambivalence was a marked contrast to the fervent crowds of the day, and of the past seven weeks.

Getting a ‘50-50’ from a former Tory voter may be some kind of progress. But that’s despite a personal, pleasant meeting with the Labour leader. And in seats like Watford, unless it translates into support on the day, it may derail even the Jeztrain.