Kieron Bryan, a 29-year old, British video journalist from London, who is one of 30 people arrested on boat Arctic Sunrise by Russia authorities at an offshore oil drilling rig on 18 September, says he fears "losing years of his life" languishing in Russian prison.

Mr Bryan's description of Russian prison where the arrested Greenpeace activists have been kept comes from a letter he wrote to the Sunday Times. In his letter, he described the treatment in prison as "ludicrous".

Apart from Mr Bryan who is a video journalist, those arrested include 28 activists and another photographer. Russia had earlier charged the activists with piracy which could have landed them a maximum sentence of 15 years. Authorities have now replaced it with hooliganism charges, which entail a maximum punishment of 7 years.

Greenpeace, has however, denied all charges and demanded that the detainees and the vessel "Arctic Sunrise" be released.

Speaking about his fears and life in Russian prison, Mr Bryan in his letter says: "My greatest fear is being kept from my family, my friends and my girlfriend for any great length of time.

"In many ways I'm lucky I don't have children who depend on me, but the fear of losing years of my life and the opportunity to perhaps start a family is terrifying," he writes

Speaking about his prison cell which is 26ft long, 13ft wide and 20ft high, Mr Bryan says his hardest moment was his first night when the group was split up and put in different cells.

"Now the difficulty is the silence and ignorance imposed by our detention," he writes.

"I spend 23 hours a day in here with nothing but the occasional book and my thoughts," he wrote. "We are granted an hour a day for exercise which is held in a shed about 30 metres from my cell. If I'm lucky I might get to shout a quick hello to an English speaker," he says.

Describing the food in prison, Mr Bryan says, lunch includes soup and a fish stew which "tastes like an ashtray full of seawater."

All 30 people, which include an Australian, who were arrested when Russian authorities stormed the "Arctic Sunrise" are currently held in pre-trial detention until 24 November.