Three environmental activists jailed for their part in an anti-fracking protest have released a video message promising they will win the battle against fracking.

The men became the first to receive a custodial sentence for environmental protests against shale gas extraction this week. Simon Roscoe Blevins, 26, and Richard Roberts, 36, were given 16 months in prison and Richard Loizou, 31, was sentenced to 15 months in jail on Wednesday after being convicted of causing a public nuisance by a jury at Preston crown court in August.

In a message that has been released as the men wait in Preston prison to be moved to jails elsewhere in the country, Loizou said he would miss everything about his life outside while serving his sentence.

But he added: “I think we will win, because this is a last-ditch attempt to squeeze the remaining fossil fuels from the earth. It is like industry clinging on to an old paradigm of the way things operate.”

In the message, Roberts recounted his part in a four-day protest that blocked a convoy of trucks carrying drilling equipment from entering the Preston New Road fracking site near Blackpool. He said he was wearing shorts and a T-shirt when he climbed on to a truck, where he remained for four days.

“I got on this lorry about 8 o’clock in the morning … I was just in shorts and T-shirt. The only reason I was able to stay up there for three days and nights was because local people handed up clothing, sleeping bags, food…”

The court heard this week that the jailing of the men meant they were the first to receive custodial sentences for environmental 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. Another defendant, Julian Brock, 47, was given a 12-month suspended sentence after pleading guilty to the same offence.

At approximately 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 on to the cab of the last lorry.

At about 3.18pm, Roscoe Blevins, a soil scientist from Sheffield, also climbed on to one of the lorries. In the early hours of the following morning, Brock also climbed on to 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. Blevins did the same at 4.45pm on 28 July, having spent just over 73 hours on his lorry. Roberts descended at 8.13pm the same day, after 84 hours. Brock did not climb down from his lorry until 29 July at 11.35am, after an estimated 76 hours.

The government overturned a decision by Lancashire county council and gave the energy firm Cuadrilla consent to extract shale gas at two wells on the site in October 2016. More than 300 protesters have been arrested since Cuadrilla began constructing a fracking pad at the site in January 2017.