The number of individuals incarcerated on terrorism-related charges in the United Kingdom has reached its highest level since records began in 2010, according to recent Home Office data. At the end of June 2026, there were 275 inmates held for terror offenses, marking a 7% increase from the 257 recorded at the same point in 2025.
The majority of those imprisoned—57%—are identified as holding Islamist-extremist views. A further 29% espouse extreme right-wing ideologies. These figures reflect ongoing concerns about diverse extremist threats facing the country.
The data also highlighted a significant rise in terror-related arrests over the past year, a trend linked to recent legal measures targeting extremist groups. Between July 2025 and June 2026, authorities arrested 3,867 individuals on suspicion of terrorist activities. Of these, approximately 3,630 arrests, or 94%, were associated with support for Palestine Action, a group that was recently proscribed.
The surge in arrests connected to Palestine Action follows government efforts to curb activities seen as promoting or supporting terrorism, underscoring the impact of the ban on the group. The Home Office figures suggest that enforcement actions are focusing substantially on this segment of suspected ideological extremism.
Overall, the data indicates a continued expansion of the counterterrorism prison population and sustained law enforcement activity targeting both Islamist and far-right threats within the United Kingdom.