Video report by ITV News Correspondent Neil Connery
A French journalist who was held by Islamic State has spoken to ITV News about life in captivity.
Nicolas Henin, who was released along with other French hostages in April this year, said the murders of former cellmates James Foley, Steven Sotloff, David Haines and Alan Henning had brought back "brutal" memories.
"Normally when you are released you are free - I'm not.
"My mind is still somewhere in a cell in Syria, and I can very much wake up one day with news that one of my former cellmates has been killed and this brings me back months before," he told ITV News' Neil Connery.
"It is very brutal."
Henin said the hostages spoke about "life, hopes and expectations" during their time together.
"We were sharing all of our lives. There is no privacy when you are stuck together in a room for 24 hours a day, seven days a week.
"We were having meals together, sleeping next to each other.
"We were having discussions about everything: life, hopes, expectations."
He also revealed that the hostages attempted to stay fit by "running on the spot" as the space in the cell was limited.
Those who had converted to Islam prayed five times a day, he added.
Among those to have converted is US citizen Abdul-Rahman Kassig who was previously known as Peter Kassig.
He was threatened by militants at the end of the video showing the murder of Alan Henning.
Henin said the 26-year-old's conversion to Islam was sincere, and reported seeing him practicing the religion "as much as he could" by praying and fasting for Ramadan.
"He thought Islam would give him the strength to deal with the difficulties of this captivity," he said.
British hostage John Cantlie appeared in another propaganda video released by IS last night.
The journalist's terminally ill father issued a message pleading for his release earlier this month.
Henin said he was "optimistic" that Cantlie's "lectures" will help save his life.
"I am optimistic that the 'lectures' that the captors have asked him to deliver will be a way for him to pay for his life," Henin said.
"I hope his captors will understand what a good guy he is."
He said he was "very close" to murdered Britons Alan Henning and David Haines - who gave him advice on how to deal with life in captivity.
He described Henning as "totally innocent", adding that the former taxi driver was "always willing to help others".
Henin said he cannot comprehend the turmoil families of hostages experience.
"Families always suffer even more than the hostages themselves.
"The worst thing is not to know anything, and not to be able to do anything.
"Families deserve a lot of respect and compassion."