Extremist prisoners to be isolated in ‘sealed units’ | Society | The Guardian
https://www.theguardian.com/society/201 ... aled-units

You can just smell the legal challenge...

Yep. The EU would never allow that...... at least on the face of it.
But then, if they're given the same rights, jobs, visitation etc, the fact that they don't mix with certain groups shouldn't be illegal.

There's nothing the ECHR that says you have to mix prisoners together in any certain way. As long as the prisoners are treated individually within the terms of convention, it's perfectly fine to have (say) a wing of a prison which houses prisoners of a certain religion or culture.