Britain's prison system is holding a record 273 individuals convicted of terrorism-related offenses, a figure that has more than doubled since 2010. As of the end of March, this number represents a 3 percent increase from the previous year and surpasses the previous peak recorded in late 2025.
Of the total, 159 inmates, or 58 percent, are held for Islamist extremist views. Another 80 prisoners, constituting 29 percent, hold far-right extremist beliefs. The remaining 12 percent, or 34 individuals, are classified under 'other' ideologies, including left-wing extremism.
The majority of those imprisoned for terror offenses, 60 percent (165 individuals), self-identify as Muslim. Twenty percent (54 individuals) identify as Christian, and 13 percent (36 individuals) report having no religion. The overwhelming majority, 80 percent (219 individuals), are UK nationals, with the next most represented nationalities being Iraqi (eight prisoners) and Iranian (five prisoners).
Notable individuals serving sentences include Hashem Abedi, brother of the Manchester Arena suicide bomber Salman Abedi, and Ahmed Hassan, the perpetrator of the Parsons Green bombing. Vitor Dias, a neo-Nazi convicted of collecting terrorist manuals, and Adam Mahmood, convicted of possessing bomb-making instructions, are also among those incarcerated.
In the year leading up to March, there were 3,061 arrests for suspected terrorist activity. A significant portion of these arrests, 2,819, were linked to supporting the group Palestine Action, which was proscribed in July of the previous year. The legality of this ban has been contested in court, with a High Court ruling finding the proscription unlawful, though this decision was later overturned on appeal.
Terrorist offenders are not subject to government plans for early release to alleviate prison overcrowding and must serve two-thirds of their sentence before being eligible for parole, subject to conditions.