Freed Al Jazeera journalist Peter Greste has described how he had to stay mentally and physically fit to survive 400 days in an Egyptian prison.
Speaking about his ordeal at the Frontline Club in central London, Mr Greste told his audience how meditation, running and studying helped him through each day of his incarceration.
Mr Greste, an Australian who was deported from Egypt earlier this month, said: "I have seen quite a few people in prison that were broken by prison. I felt I had to make a conscious decision to stay fit, physically fit, psychologically fit. The greatest danger is your own mind."
He said he would start the day with meditation, would do some running and even started a distance master's degree in international relations.
Mr Greste also spoke about his colleagues Mohamed Fahmy and Baher Mohamed, who are facing a re-trial. They are currently on bail pending their next hearing on Monday.
All three journalists from the Al-Jazeera English network were jailed on terror charges in a case which the international community and civil rights groups denounced as a sham and an attack on media freedom.
Mr Greste said he hoped his colleagues would soon be cleared.
Mr Greste also described how important the campaign was in keeping their plight on the international agenda.