An elderly woman, wrapped up against the wind, stops to chat in Royton’s drab, 1970s town centre where Ukip has set up home ahead of the forthcoming by-election.

“They’re not for us any more,” she says of Labour. “I’ve always voted for them. But this time I’ll either not vote at all or I’ll go Ukip.”

Others make the same point a bit more forcefully. “I’ve had enough. They’re not on our side,” says 81-year-old Alan, a retired grandfather who voted for Thatcher and Blair but is now a signed-up ’Kipper.

Seeing a soulmate in the party’s down-to-earth Mancunian candidate, he adds: “We’ve got enough of these bastards over here. They don’t share our values. You never see them in the pub, do you?”

Ukip’s man – Stockport-born by-election veteran John Bickley – splutters about the virtues of “Australian-style immigration”. “We should welcome people from all over the world,” he begins to say. “No, we bloody shouldn’t,” says Alan, looking at his man in puzzlement. “Anyway, you’ve got my vote, sir.”

The rise and rise of Ukip – the new party of the protest voter Show all 3 1 /3 The rise and rise of Ukip – the new party of the protest voter The rise and rise of Ukip – the new party of the protest voter 30-ukipprotest-gt.jpg Onwards: UKIP are hoping to take off Getty Images The rise and rise of Ukip – the new party of the protest voter 30-ukipprotest2-gt.jpg UKIP's Rotherham candidate Jane Collins Getty Images The rise and rise of Ukip – the new party of the protest voter 30-ukipprotest3-gt.jpg In 2010, leader Nigel Farage was injured when the light aircraft he was travelling in crashed Getty Images

Time and again, as we stand outside Ukip’s “pop-up” HQ, we hear the same message – “Labour isn’t for us any more”.

Royton is one of a number of little towns that make up Oldham West – the constituency with the misfortune of a by-election to contend with this Thursday. The area is invariably described as “deprived” – and for good reason. The average salary in the constituency is £17,000.

Almost 20 per cent of the population are Asian, the families of Pakistani migrants who moved to Lancashire before the mills closed. But that is not a fair description of the area: it’s a place of 1930s semis and bungalows, Ford Focuses and white vans. Most people are in work and own their own home.

Yet, it’s not as good as it was – despite the brand-new hospitals and schools built under Tony Blair. It has been rock-solid Labour for almost half a century until its long-serving MP Michael Meacher died in October, aged 75. He had won and held the seat for almost 45 years – winning the last election with a 14,738 majority. And yet Ukip seriously fancies its chances.

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“It feels just like Heywood and Middleton,” says the party’s campaign director Paul Oakden, harking back to the by-election near-miss in 2014 when Labour clung on by 600 votes. “Except,” he says, “this time I’d say we’re two or three days ahead of where we were then.”

Anything like the same result would be a disaster for Labour. A defeat is unthinkable. It would be a catastrophic loss from which Jeremy Corbyn would struggle to recover.

His brand of anti-war socialism was supposed to appeal most of all in seats such as Oldham. And yet, only 11 weeks after his election, it is Mr Corbyn himself who is proving the biggest threat to Labour’s majority. The party’s candidate – the bright and likeable Oldham boy-done-good Jim McMahon – admits his leader had been an issue “on the doorstep”, as politicians refer to real life.

Mr Corbyn’s obfuscation on shootto-kill has cut through. “It does get raised, yes. If you knock 10 doors, you might hear it on the 10th door,” says Mr McMahon.

A senior shadow cabinet minister later tells me: “If Ukip had gone harder on shoot-to-kill, we would be in a worse position.”

Mr McMahon, 35, the leader of Oldham town council, insists it does not worry him too much. Watching him work the terraced streets in Chadderton – another of the small former mill towns in the constituency – you can see why. He’s happy in the town. He knows the people – and likes them.

“I don’t just want to be an MP. I want to be the MP for Oldham,” he tells each and every person who answers the door. He mentions his wife, who works in a coffee shop in the town, and his children, who go to school nearby.

Ukip’s candidate John Bickley, on the other hand, is “from Cheshire”. In Oldham this means he’s posh – and Mr McMahon is not shy about mentioning it.

The people who open the door to Mr McMahon are friendly. Yet there is a slight shiftiness, as if they don’t want to let him down – but might.

Ukip’s candidate senses he’s on to something after losing his three previous by-election battles. He tells me: “Corbyn is pretty toxic in a general sense round here.”

His website distils his election pitch: “I used to believe in Labour. I thought that the Labour Party believed in representing the hard-working people of our country. Far from believing in the people of Britain, Corbyn’s Labour Party would rather sympathise with the IRA than sing our national anthem to honour our brave armed forces.”

Nigel Farage is heading to Oldham on 29 November and will stay until the election. Mr Corbyn, in contrast, cancelled his planned visit on 27 November and is unlikely to visit again. Perhaps this is a blessing in disguise. It is telling that Ukip features Mr Corbyn on almost all its leaflets while Labour keeps him away. In fact, one of Mr Bickley’s leaflets has a giant picture of Mr Corbyn, such is his value to Ukip.