One of the British members of the Greenpeace Arctic 30 contemplated suicide while in a Russian prison facing 15 years in jail for charges of piracy, according to a new book.

Freelance videographer Kieron Bryan was one of a group of 30 activists and journalists arrested by the Russian military who boarded a Greenpeace ship in September 2013 after they staged a protest on a Gazprom oil rig in the Arctic.

While imprisoned in the Russian port city of Murmansk in the Arctic circle, Bryan wrote to his girlfriend Nancy telling her not to wait for him if things went bad.

“My big fear was missing out on having a family because being 44 in 15 years I would’ve lost the person I wanted to marry, lost my career, the people I love, and every semblance of joy and success I’ve had would be totally obliterated by this 15 years of darkness. I actually remember thinking I won’t make it 15 years. I honestly didn’t think I’d get that far. Would I top myself? Yeah, I think I probably would.”

The account is revealed in a new book, Don’t Trust, Don’t Fear, Don’t Beg, which takes its title from a Russian prison motto. Author and Greenpeace campaigner Ben Stewart explores a world of hardship and insecurity in a brutal penal system controlled by mafia bosses, a Gestapo-admiring governor and rife with threats of indiscriminate violence.

“I’d done a few nights in prison in various places, but Banbury police station is a fair bit different from Murmansk SIZO-1 isolation jail in the Russian Arctic,” Stewart, who was the head of Greenpeace’s media campaign to secure the Arctic 30’s liberty, told the Guardian. “The biggest difference would be the sense that they are not actually caught up in a legal process, they are caught up in a political process and so you don’t know where the levers lie to get you out. It doesn’t matter whether you’re guilty or not. So it’s the powerlessness, the hopelessness, that really affected them.”

Russian activist Dimitri Litvinov was particularly singled out for his dissident family history - he is the fourth generation of his family to be jailed by the Russian government. He was hauled into punishment cells and threatened by agents from the FSB - formerly KGB - intelligence bureau. Litvinov was also subjected to the philosophical treatises of the prison governor, who told him: “History has been so unfair to the Gestapo... Those guys knew how to run a prison.”

“It was not predictable who would cope better,” said Stewart. The female activists, unlike the men, were held in isolation cells. They maintained their sanity by tapping out excruciatingly slow sentences to one another (one tap for ‘A’, two for ‘B’) on the exposed pipes in their cells.

In the male cells, the activists negotiated a complicated system of competing interests. Some of them were told they were under the protection of mafia bosses who thought they had been dealt with unfairly by the Putin regime. But they were warned against misdemeanour and told that prison justice was meted out in boss-sanctioned violence.

Cigarettes, mobile phones, consumables and other contraband were traded, messages sent and debts paid via a system of plastic bags spun into ropes rigged between cell windows each night. Some of the messages, known as ‘wet letters’, were traded between the male and female wings of the prison.

Frank Hewetson, an English career activist, told Stewart he’d suffered a panic attack when he first discovered he may end up in jail for the next 15 years.

“He got driven at speed to the hospital in Murmansk,” recalled Stewart, “and an armed guard pushed him around the hospital looking for the chief psychologist in a wheelchair, while crooning Depeche Mode songs in his ear and checking the safety catch on his gun.”

“Good luck, my Depeche Mode friend,” said the guard as Hewetson was discharged.

After three months of exhaustive diplomacy and media attention, the Putin government relented and granted the activists amnesty. Stewart spent the following two months collecting their stories, including Bryan’s, who is now married to Nancy.

The period of Arctic 30’s incarceration was a crisis for both the Russian Greenpeace office and Greenpeace International. Their Russian employees were branded “enemies of Putin”, said Stewart. “The office in Murmansk was broken into by knife-wielding thugs in masks. They were photographed, they were followed, they were bugged.”

Russia’s oppressive response caught Greenpeace by surprise. “No-one would have known really, I don’t think, that it was going to be that one, that mission, that ship, that was going to be the biggest Greenpeace story since the sinking of the Rainbow Warrior,” he said. “There were questions about whether Greenpeace should have known that this would have been the reaction from the Russian state.”

However Stewart believes Greenpeace is currently facing a bigger crisis in India than it did during the Arctic 30 affair. Last week the Indian government froze Greenpeace India’s bank accounts in a move Greenpeace said could bring its operations in that country to a halt. India has accused Greenpeace of “misreporting their funds and using their unaccounted foreign aid to stall crucial development projects”.

On Tuesday, 182 civil society organisations and prominent individuals delivered a petition to the Indian ministry of home affairs asking them to reopen Greenpeace’s bank accounts. On the same day, the Economic Times reported that India’s intelligence bureau had asked the tax office to revoke Greenpeace’s charity status.

“This is a multi-pronged attack on Greenpeace India,” said Samit Aich, the executive director of Greenpeace India.

“When we are not able to pay the rent on the building and that runs out and unable to pay people’s salaries, then effectively we won’t exist there,” said Stewart. “What the Russian government did [during the Arctic 30] was pretty insidious if you look at the kind of pressure that the staff were under there... But the assault on the Indian office has as big, if not bigger implications for the organisation.”

Greenpeace has challenged Indian government plans to develop its energy sector through a series of controversial projects. Aich said there was a concern that if a democratically-elected government could bully Greenpeace in this manner it could spark a cascade of similar actions from other governments that find their activism inconvenient.

“For global Greenpeace this is one of the bigger [crises] if not the biggest one. It certainly is unprecedented, either in terms of its scale or in terms of the impact to the organisation globally,” he said. “It may give cues to other countries to do similar acts to organisations like Greenpeace.”

Proceeds from Stewart’s book, for which advances of £40,000 have already been paid, will go to environment organisations Platform, 350.org and Greenpeace and Russian prisoner advocacy groups Agora and Human Corpus.