There is a "significant risk" of Islamic radicalisation behind bars the head of the prison and probation service has told BBC Panorama.
Michael Spurr the chief executive of the National Offender Management Service of England and Wales (NOMS) told the programme:
"There is a significant risk, given the fact that we manage some very dangerous people.
"Our job is to minimise that risk becoming a reality - that somebody in prison becomes radicalised and commits a terrorist offence."
Over the last ten years the number of Muslims in prisons in England and Wales has doubled, with the figure reaching 11,729 in 2013.
There are about 100 al-Qaida-inspired Islamist terrorists behind bars.
More top news
Flooded in January, farming-driven Malawi ends 2015 facing its worst drought for more than 20 years. And now a slower tragedy is unfolding.
A hapless burglar has died from smoke inhalation and thermal burns after getting stuck in a chimney while trying to rob a house.
From the canals of Venice to a remote island in the Pacific Ocean, the effects of climate change are worryingly visible across the globe.