You would expect most political candidates who pull off a shock win to celebrate their victory, maybe with a glass of bubbly and excitement for the challenges of elected office ahead. But on Friday, as thousands of new councillors celebrated their triumphs, some surprise victors were less than pleased.

Green party handlers apologised to one newly elected councillor in Finsbury Park, north London, put down as a “paper candidate”, who pulled off an unexpected win. “You’re going to be great, we’ll support you,” they said, according to the Islington Tribune.

A paper candidate is someone who is fielded on the understanding that they are highly unlikely to win, to enable a party to appear on the ballot paper in as many places as possible. Reform UK were so keen to enlist candidates across the country that the party cold called members of the public – including a Guardian journalist – asking them to run. But this year’s local elections, which saw Labour’s worst results on record, meant many new candidates were elected.

In Camden, a byelection is already on the cards after a secondary-school teacher who was elected for the Greens immediately quit as councillor because he is not allowed to hold the post while also teaching in the borough.

So, what is it like to pull off a surprise win? Tyrone Scott has been a member of the Green party for 12 years. Four years ago, he was tantalisingly close to power, losing his race to become a Hackney councillor by 27 votes. “It was quite devastating at the time,” the 34-year-old said. Months later, he ran for deputy leader of the party but came second to Zack Polanski, who has since become leader.

He retreated from politics to take a job at a charity. “It looked like it was difficult for me to run again, I had quite a lot of work commitments,” he said. He still wanted to run so as a compromise, opted for an area where there was “less likelihood we were going to win”. He was selected in Hackney Wick, where the Labour party sailed to victory last time the seat was contested in 2022. Nonetheless, he called himself a “cardboard candidate” rather than a paper one, because the party thought victory was possible everywhere in the borough.

Activists “did a very small amount of canvassing” in Hackney Wick compared with the rest of the borough where it had run year-long campaigns.

The first indication that things might be better than expected was the large pile of votes for his ward at the verification on Thursday. “I had a little feeling but, even then, I didn’t really believe it,” Scott said. Things crystallised at the count when the Greens pulled of win after win early on. “The first nine or 10 seats rolled through as all Green, including a couple of unexpected ones,” he said.

In a seismic day for the Greens in London, the party won a majority on Hackney council, ousting Labour as the controlling party for the first time since 2002, winning 42 of the 57 seats up for grabs. Zoë Garbett became the borough’s first Green mayor, loosening Labour’s 24-year grip on the post.

When the results of his ward were announced and all three councillors elected were Greens, Scott said it was a “mix of emotions”, including some “nervous excitement”.

“I thought there was a minor chance but not at all to have got three across the board,” he said. “It felt quite surreal and we were very elated. I think all of us are having a moment of, ‘Oh, wait, this is real now’.”

Scott works as head of campaigns for an anti-poverty charity. He told his bosses about his intention to stand, who said he could “go for it” on the “understanding that I was less likely to get in”. In the event he did win, his workplace said they could work around it. “I’m sure now they’re thinking: ‘Oh actually, it’s real’, and we’ll have a conversation when I get back to work on Monday,” he said.

Scott hopes the Greens can rebuild “community cohesion” in Hackney and show that, especially in light of Reform UK’s gains across the country, “we can be a shining example of how to build hope rather than hate”.