Thirteen protesters who chained themselves to railings at Heathrow Airport, causing flights to be cancelled, will be sentenced today.
The campaigners, members of the Plane Stupid lobby group, were told by a judge following their trial that it was "almost inevitable" they would go to prison. They could be handed jail terms of up to three months.
Shadow chancellor John McDonnell, whose Hayes and Harlington constituency includes Heathrow, has said jailing them would be a "disgrace" and Green MP Caroline Lucas is expected to attend a rally outside Willesden Magistrates Court before the hearing.
Following a week-long trial at the same court in January, the demonstrators were found guilty of aggravated trespass and entering a security-restricted area of an aerodrome.
The group cut a hole in a fence and made its way on to the north runway at Heathrow in the early hours of July 13 last year as part of the long-running Plane Stupid campaign to end airport expansion.
Their actions caused "astronomical" financial cost and disruption for thousands of passengers, with 25 flights cancelled.
District Judge Deborah Wright warned them it was "almost inevitable" they would all receive custodial sentences.
One of those convicted, Danielle Paffard, 28, of Blenhiem Grove, Peckham, south-east London, said the prospect of going to jail was "terrifying".
Speaking after the verdict, she said: "Climate change is the most pressing issue of our time and hundreds of thousands of people are dying already and it's going to get worse and so we stand by the actions we took."
Alongside Ms Paffard, those convicted are Rebecca Sanderson, 28, of Newton Road, Machynlleth, Powys; Richard Hawkins, 32, and Kara Moses, 32, both of Heol y Doll, Machynlleth, Powys; Ella Gilbert, 23, of Magdalen Street, Norwich; Melanie Strickland, 32, of Borwick Avenue, Waltham Forest, north-east London; Graham Thompson, 42, of Durlston Road, Hackney, north-east London; Sheila Menon, 44, of Pellerin Road, Hackney; Cameron Kaye, 23, Edward Thacker, 26, Alistair Tamlit, 27, and Sam Sender, 23, all of Kenwood Close, Sipson, West Drayton, west London; and Robert Basto, 67, of Blackborough Road, Reigate, Surrey.
All 13 were released on unconditional bail to return for sentencing.