Greg Collins, a 53-year-old care worker, waved off the bright turquoise open-topped Brexit party bus as it began one of its final grand tours of the Brecon and Radnorshire constituency and declared that Nigel Farage’s candidate would be getting his vote.

“I was a Labour supporter for a long time but they have let us down – Tony Blair lied over the Iraq war,” said Collins. “The Lib Dems helped bring austerity on us so I won’t have anything to do with them.”

And the Tories? Collins, it turns out, was one of 150 or so people who stood in the drizzle outside Brecon Guildhall this week hoping to get a glimpse of the new prime minister when he visited mid-Wales before Thursday’s byelection. But the crowd was left disappointed, with Boris Johnson only making a flying visit to an enterprise park on the fringe of the town rather than meeting and greeting the voters.

Facebook Twitter Pinterest Boris Johnson arrives at the offices of the BVG Group in Brecon during his visit to Wales. Photograph: Jacob King/PA

“I was keen to see him and if I’d have had the chance I’d have liked to speak to him,” said Collins. “I waited there for nearly two hours and he didn’t turn up. The common man gets stiffed all the time. I’m voting for Mr Farage this time and if he turns out to be a liar, I won’t vote again.”

In truth, the byelection is just about the last thing Johnson needs. It is his first major test as prime minister and if, as is widely expected, the Liberal Democrats win, his working majority in the Commons will be reduced to just one.

The byelection was called after the sitting Conservative MP Chris Davies was embroiled in an expenses scandal that resulted in him being ousted when more than 10% of the registered voters signed a petition to remove him. To the surprise of many Davies was re-selected to fight the byelection for the Tories.

The Brexit party candidate, Des Parkinson, a former police chief superintendent, called the Tory decision to put Davies up again as arrogant. “He’s doing the Tory cause here no good.”

Facebook Twitter Pinterest Brexit party supporter Diana Coad. Photograph: Gareth Phillips/The Guardian

Activists for the Brexit party have flooded in. Diana Coad, a Tory defector from Berkshire, was running the buzzing Brecon campaign office on Wednesday – and making sure those getting on the bus had been to the toilet before departure. “They’re a smashing bunch. They come from all over,” she said.

One absentee is Farage. The Brexit party MEP Nathan Gill explained that the leader was spending time in the US “with his friend Donald Trump” and also planning a much larger campaign.

“We’re in general election mode,” said Gill. “He’s got to make sure we’re fighting fit and ready for the big one.” Gill said he thought there would be a general election on 24 October. “Put a fiver on it.”

Quick guide Brecon and Radnorshire byelection Show Hide Why was there a byelection? A petition to recall the Conservative MP Chris Davies secured the signatures of more than 10% of registered voters in the constituency. Davies was convicted for submitting fake expenses documents invoices for nine framed landscape photographs, costing £700, to decorate his office in Builth Wells. He was fined £1,500 and ordered to complete 50 hours of community service. He stood again for re-election. How did the parties do at the last election? In 2017 the results were as follows: Christopher Davies (Cons) 20,081 (Maj 8,038)

James Gibson-Watt (Lib Dem) 12,043

Dan Lodge (Lab) 7,335

Kate Heneghan (Plaid) 1,299

Peter Gilbert (Ukip) 576 What were the 2019 results? The Liberal Democrats took the seat from the Conservatives: Jane Dodds (Lib Dem) 13,826 (Maj 1,425)

Christopher Davies (Cons) 12,401

Des Parkinson (Brexit) 3,331

Tom Davies (Lab) 1,680

Lady Lily the Pink (Monster Raving Loony) 334

Liz Phillips (Ukip) 242

Of course, not everyone was impressed by the bright blue bus and the Brexit party bluster.

Les, a sheep farmer, was taking his ease in the sunshine when the vehicle drove through Brecon town centre. “They’re the sort that are here today, gone tomorrow,” he said.

Agriculture has been at the centre of this campaign with warnings of heartache for sheep farmers and even civil unrest if the UK leaves the EU with no deal.

Facebook Twitter Pinterest Liberal Democrats organise their byelection campaign in Brecon. Photograph: Gareth Phillips/The Guardian

Les voted for remain and will be backing the Lib Dems at the byelection. “Boris is thinking he can get a deal. I very much doubt he can. With him in charge we’re heading for a no deal. That’s a bad job for us. All the work we’ve done will be undone. It will mean a big adjustment.”

Three doors along from the Brexit party office, the Lib Dem campaign HQ was even more lively. The Lib Dems held this seat between 1997 and 2015 and believe they will win it back.

Candy Piercy had just arrived from Buckinghamshire to help the party’s candidate Jane Dodds. A veteran of byelections up and down the country, Piercy said she was shocked the Tories had chosen Davies to stand again. “I wonder if it’s because they want to blame him for losing it,” she said.

Kirsty Williams, the Lib Dem Welsh assembly member for Brecon and Radnorshire, said the campaign was not just about farming and Brexit.

Facebook Twitter Pinterest Jane Dodds canvassing in Crickhowell, Wales. Photograph: Gareth Phillips/The Guardian

“People want to talk about hundreds of different things,” she said. “Each doorstep conversation can be very different to the one before. Some people are talking about Brexit. We’re a very rural large farming industry. [A] no deal would be catastrophic for our sheep industry. Lamb and beef prices are down already. Farmers are feeling the strain.

“But when they are not talking about Brexit they want to talk about public expenditure, about infrastructure, austerity and hyper-local issues such as is the library going to survive.”

Williams criticised Johnson’s no-show in the town centre – a stark contrast to the efforts of the new Lib Dem leader, Jo Swinson, who has visited four times.

Facebook Twitter Pinterest Tory candidate Chris Davies: ‘The support I’ve had from the people of Brecon and Radnorshire has been immense.’ Photograph: Victoria Jones/PA

“Quite clearly this was a very stage-managed visit with extensive care taken to avoid scrutiny,” she said. “In a constituency particularly vulnerable to no-deal Brexit, local people are right to expect the Conservatives to explain why they are pursuing it. The fact they shied away speaks volumes.”

Davies, however, said he did not regret standing. “The support I’ve had from the people of Brecon and Radnorshire has been immense,” he said. “These aren’t just constituents. They are former clients, friends, family. It was they that encouraged me to stand again.”

He insisted he had not meant to commit an offence over his expenses – which concerned the submitting of fake invoices for nine framed landscape photographs, costing £700, to decorate his office in the town of Builth Wells.

“I regret making a mistake, clearly. A mistake was made in my paperwork. This was a legitimate expense. There was no financial gain. It was a pure mistake and I’ve paid a heavy price.”

Asked whether he was sorry for causing his new leaders such a headache, he said: “There are many things the prime minister will have a headache over. I’m sure this byelection is one of them.”