You hear the Jeremy Corbyn rally before you see it. In Islington, the Labour leader’s home constituency, the sound of the megaphone drifted over the quiet back streets. Indeed, if you have spent the last few weeks reading about the Trotskyist entryists taking over the party, it might seem like the perfect metaphor. Infiltration, of an audible kind.

The reality was far more benign. Highbury Fields is an elegant, tree-lined park in a desirable, Georgian square. The Black, Asian and minority ethnic (BAME) rally took up roughly a third of the grass. While some of the crowd clustered around Corbyn’s signature fire truck, some families had settled down to watch the warm-up speakers from afar, and toddlers danced in the summer sun. There were even camping chairs and a picnic.

On the night of Corbyn’s post-Brexit showdown with MPs, the rally in Parliament Square bristled with signs attacking MPs as “Blairite plotters”. But not here. A few signs said: “Migrants and refugees welcome”. Others backed Corbyn “for health, education, jobs”. A speaker reminded that there were plenty of signs left over if they wanted to grab one for a post-speech “family selfie”.

Corbyn supporters have been portrayed as everything from opportunistic Greens to fervent followers of a cult. Some attendees were clearly desperate to see the man himself – as the evening shadows lengthened, one heckler plaintively demanded: “Where’s Jeremy?”

But most of the attendees I spoke to were Labour members. One, the solicitor Nazir Ahmed, was vice-chair of a constituency Labour party in London’s east end. He said: “I think Corbyn is the right person to lead the Labour party.

“He is a man who is honest in politics, speaks his mind, sticks up for what he believes and I think he should be given a fair chance to go into an election and see if the British public will give him a mandate.”

Saidu Kumara, a 22-year-old graduate, had come along with a university friend. He had joined Labour in 2012, and liked Corbyn’s promise to abolish tuition fees.

But he did worry about the chances of winning a general election: “They are going to have to win some of the swing voters. I have some concerns.”

Indeed, Corbyn’s rally, even on his home turf, did not look like the bustling London high street nearby. It was younger and, even at this BAME rally, whiter. Everyone I spoke to had a degree. While listening quietly to the speeches on racial inequality, they seemed mostly drawn to Corbyn’s critique of austerity, and the idea of an alternative economic plan.

When Corbyn himself eventually popped over the parapet of the fire truck, he received the warmest applause of the evening (clappers outnumbered chanters in this crowd). He attacked Labour MPs who abstained on last year’s Welfare Bill (boos) and promised investment in education and the NHS (cheers). And then, suddenly, it was over. With evident practice, Corbyn came down from the fire truck just long enough for the promised family selfie and then vanished into a black car. As it sped away, the fire truck blasted upbeat reggae. Suddenly, everyone was dancing.

Khadija Mohamed, a management consultant, was one of those who stayed to the end. She hadn’t previously been a Labour supporter – she had never even voted before. She didn’t read newspapers, or listen to the news on the radio. She gets her news about the Labour party from Corbyn’s Youtube channel and Twitter.

But she paid £3 to vote for Corbyn in 2015, joined the party and paid £25 to vote again. “My friends don’t care about politics,” she said. “But when I told them what he is about they go, ‘oh’.

“People care about other people, not just themselves. The challenge for him is how does he get his message to more people who don’t generally hear equality and stuff like that.”

The light was fading, but the music in the park gave the neighbourhood a festive feel. The fact is, Corbyn just makes many Labour supporters feel hopeful, and happy. Even, to use a buzzword, aspirational. "Are you ready to hear the good news?" one rally speaker asked. If Labour's rebel MPs want control of the party back, they'll have to find a way to match that.