The boss of MI5 has described the rise of children being investigated for terrorism in the UK as "staggering" as he warned of "canny online memes" drawing them into extreme right-wing ideologies.Director-general Ken McCallum said the security agency was seeing "far too many cases where very young people are being drawn into poisonous online extremism".

The boss of MI5 has described the rise of children being investigated for terrorism in the UK as "staggering" as he warned of "canny online memes" drawing them into extreme right-wing ideologies.Director-general Ken McCallum said the security agency was seeing "far too many cases where very young people are being drawn into poisonous online extremism".