Four anti-fracking activists face being the first environmental campaigners to be jailed for a protest in the UK since 1932, according to a lawyer representing one of them.

Simon Roscoe Blevins, 26, Richard Loizou, 31 and Richard Roberts, 36, were told by a judge to expect custodial sentences after being convicted of causing a public nuisance by a jury at Preston crown court in August. Another defendant, Julian Brock, 47, pleaded guilty so did not face trial.

The four men were charged after taking part in a four-day direct action protest that blocked a convoy of trucks carrying drilling equipment from entering the Preston New Road fracking site near Blackpool.

A sentencing hearing on Tuesday at Preston crown court heard arguments from Kirsty Brimelow QC that the men would become the first environmental activists to receive jail sentences for a protest in the UK since the mass trespass on Kinder Scout in the Peak District in 1932, which marked the beginning of the right-to-roam movement. Activists have previously been given jail sentences for breaching court orders and not paying fines.

Around 8am on Tuesday 25 July 2017, as seven lorries containing drilling equipment attempted to approach the site, Roberts, a piano restorer from London, got through a police cordon and climbed on top of the first lorry, bringing the convoy to a standstill. Loizou, a teacher from Devon,climbed onto the cab of the last lorry.

At around 3.18pm Blevins, a soil scientist from Sheffield, also managed to climb onto one of the lorries. In the early hours of the following morning Brock, from Torquay, also climbed onto a lorry in the convoy.

Fellow protesters threw blankets, food and water up to the men as they camped out on the vehicles. Loizou came down on 27 July at 5.10am after 45 hours 6 minutes on the lorry and was arrested. Blevins did the same at 4.45pm on 28 July, having spent 73 hours and 27 minutes on his lorry.

Roberts descended at 8.13pm the same day, after 84 hours 19 minutes. Brock did not climb down from his lorry until 29 July at 11.35am, after an estimated 76 hours and 6 minutes.

The energy firm Cuadrilla, which has received government consent to extract shale gas at two wells at Preston New Road, has said fracking is likely to start in the next few weeks. The company confirmed that 28 lorries had brought fracking equipment to the site on Monday.

Speaking for the prosecution, Craig MacGregor said the police argued that the demonstration resulted in significant travel disruption, causing the road to be closed initially until a contraflow was established. Police said local residents had seen disruption to their lives and local businesses had a loss of trade.

MacGregor said lorry drivers had to stay with their cabs and were unable to return home. He said the protest had cost the police £12,000 and Cuadrilla around £50,000.

Brimelow , head of the international human rights team at Doughty St Chambers, representing Roberts on a pro-bono basis, stressed to the judge that it had been a peaceful and political protest. She said that the right to freedom of speech went beyond “simply standing and shouting” and extended to non-violent direct action.

Brimelow said the fact that central government had overturned a decision by Lancashire county council to reject Cuadrilla’s fracking application demonstrated that “political process has been exhausted”. She added that the judge, Robert Altham, should bear in mind that “there has been no environmental protester sentenced to jail since 1932”.

About 60 people gathered outside Preston crown court on Tuesday morning to support the men – who have become known as “the Frack Free Four” – wearing red roses and holding anti-fracking banners.

Isabelle Luterbacher, a yoga instructor from Devon who travelled to Preston to show support for Loizou, said: “I’m already feeling very emotional. We all are. We’ll all be devastated if it comes to a custodial sentence.”

Speaking outside court, Miranda Cox, an independent councillor in Kirkham town, said: “People have come down to show their support and love for four men who behaved honourably in taking direct action last summer.

“They answered a call for national solidarity to help support the people of Lancashire who have for seven years been campaigning and doing everything possible within their capabilities to fight fracking.”

The hearing will conclude on Wednesday.

• This article was amended on 26 September 2018 to make it clear that the claim that the men would be the first environmental protesters to be sentenced to jail since 1932 was made in argument in court by one of the defence lawyers.