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John Shelly said he saw the reality of Islamic radicalisation grow from nothing during 15 years spent in more than 40 UK prisons.

He was jailed for armed robbery in 1999, since when he said he had heard increasingly vocal support for "terrorist groups... like IS"

Islamic radicalisation in England's prisons is getting worse because of staff shortages and a crisis in the penal system according to the former head of the National Counter Terrorism Security Office.

John Shelly gave his account to the Today programme's Sima Kotecha.