A record number of terrorists are now behind bars in Britain, according to new figures, with more than half of those in custody holding extreme Islamist views.By the end of March, there were 273 criminals in prison for terrorism - the highest number since records began in 2010, when the number stood at 126.The number is up three per cent year-on-year and has surpassed the peak recorded at the end of 2025 at 267 behind bars.The “vast majority” he…