They came, under cover of darkness, to save the planet by shutting down Stansted. There was the grandson of a peer who served in Wilson’s Cabinet, a film animator and a hat designer, not to mention the undergraduates and postgraduate research students.

This was, in the words of one campaigner, “designer direct action”, and those taking part were adamant that there was no time to lose in tackling the peril of climate change. Tilly, 21, explained: “If we fail, it will be the people on this runway, and our children, who’ll live with the consequences.”

Inside the departure lounge would-be passengers were dealing with the more immediate consequences of her actions. By the end of the five-hour Plane Stupid protest, 57 people had been arrested and 52 flights cancelled, leaving thousands grounded.

With the public inquiry into expansion of Stansted due to open next spring and a verdict on a third Heathrow runway expected next month, campaigners gave warning that the middle classes were angry, and direct action could become a recurrent problem for airlines and passengers unless the sector’s growth was checked.

Times Archive, 1967: Stansted protesters

The demonstration began at Stansted itself, when a specially chartered train filled with 400 local people pulled out for London

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At Stansted yesterday the activists cut through the perimeter fence at about 3am, while the runway was closed for maintenance. Lily Kember, 21, an anthropology student, said that the group used boltcutters to get into a secure area about 50 yards from the runway. “Being arrested is a terrifying prospect, but not nearly as terrifying as the threat of climate change,” she said. Her mother said: “We know what she does and we stand by her.”

The protesters, some wearing high-visibility vests with “Please DO something” printed on them, chained themselves to security fencing, so that police had to remove them physically.

Last night, five people were charged with aggravated trespass. Another seven were released on police bail without charge pending further inquiries, after being arrested on suspicion of public disorder offences. More than 40 others remained in custody, a police spokesman said.

BAA, the airport operator, said it would learn any lessons that emerged from the breach, but the GMB union said that it had been pressing for a security review.

Ryanair, Stansted’s largest airline, described the disruption as unacceptable and called for an investigation into why BAA had failed to keep the airport “secure and open”. Thousands of passengers were also frustrated. Anita Kelleher was due to fly to Ireland for her father’s funeral, but her flight was cancelled: “His funeral is tonight, the Rosary is tonight. I’ve missed being at my dad’s Rosary tonight and I’m heartbroken.”

Trine Maaetoft, who was supposed to fly to Denmark with her two toddlers, had sympathy for the protesters’ cause but not their methods: “Flying is the only option for me. My sister has had a baby and this is my only trip home, instead of Christmas. It’s not the way to get people on your side.”

Maggie Thorburn, of the anti-Heathrow expansion group Hacan, gave warning that the Stansted protest might be the shape of things to come: “Hacan is not a direct action group, but we are encouraged to see that the passion is there. I wouldn’t be surprised if there were other direct actions before next month’s Heathrow announcement.” She added that “a couple of direct action training sessions” had been held near Heathrow. “It is the middle-of-the-road, middle-aged lady who will be on the warpath, reluctantly but in desperation.”

Joss Garman, 23, the grandson of a pilot, who founded Plane Stupid, said that yesterday’s protesters were “not the sort of people who usually go in for activist stuff”, adding that they were “educated, scientifically literate, passionate and eloquent”.

Mr Garman, who did not go to Stansted himself, said that people of his age who were drawn to Plane Stupid were “the Iraq generation who grew up trying to stop the war” and had now turned to peaceful direct action after their lobbying of politicians in that case fell on deaf ears.

Nick Barton, commercial and development director of Stansted Airport, said that there was never any possibility that the intruders could have reached the runway. “At no time were any passengers or planes in danger,” he said.

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