Director General of MI5 Sir Ken McCallum delivers the annual Director General's Speech at Thames House, the security service's headquarters in London, on Thursday October 16, 2025. Jonathan Brady/PA/AP

The United Kingdom has seen a 35% rise in the last year in the number of suspects investigated annually for possibly working for a hostile foreign government, the head of the UK’s domestic security service, MI5, said in a speech Thursday.

In the service’s annual update on threats facing the UK, Ken McCallum said, “A more hostile world is forcing the biggest shifts in MI5’s mission since 9/11,” and that his “teams are currently running near-record volumes of investigations.”

Opening his speech, McCallum expressed sympathies for the two people killed in an ISIS-linked attack on a synagog

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