MI5's key workers are being tasked with safeguarding national security as it tries to maintain staff levels inside its headquarters building at Thames House with social distancing. Credit: Wikipedia.

When you are head of Britan’s MI5 secret Service, there is never a dull moment.

“When my phone rings late in the evening my stomach still lurches,” said Ken McCallum, the new director general — historically known as “C.”

A slim, youthful Glaswegian mathematician by training, he likes hiking up mountains when his parenting and work allows.

We don’t know if he’s signing his documents in green ink, as Sir Mansfield Smith-Cumming did, but we do know he’s facing a “nasty mix” of national security threats, BBC News reported.

Russian, Chinese and Iranian espionage and disruption is all growing in severity and complexity, a relaxed McCallum said at his first media briefing.

Fast-growing right-wing terrorism remains the biggest threat — with Northern Irish and Islamist extremism also a concern, BBC News reported.

To make matters worse, the ongoing Covid lockdown has raised the risk of online contact between groups, and made covert surveillance harder, he added.

Fewer crowds give adversaries fewer opportunities to attack but make the job of MI5’s watchers more conspicuous.

“We spend our days and nights planting microphones in attics — with warrants — and meeting covert informants,” said McCallum, a 24-year MI5 veteran, “so we are used to operating in secret with extreme care.”

McCallum said the UK faced threats “up to and including assassinations, as the Alexei Navalny poisoning reminds us; threats to our economy, our academic research, our infrastructure and, much discussed, threats to our democracy.”

Ken McCallum led counter terrorism investigations during the London 2012 Olympic Games and MI5’s response to the attempted assassination of former Russian spy Sergei Skripal in 2018. Credit: MI5 Handout.

But the agency has drawn its share of criticism.

Some in Westminster have argued that MI5 needs to refocus on countering China and Russia, The Guardian reported.

Over the summer, parliament’s watchdog intelligence and security committee accused the spy agencies of “taking their eye off the ball” when it came to Russian activities in the UK.

McCallum insisted that jihadist plots still form the bulk of UK investigations, pointing out there are still tens of thousands of people committed to that ideology, BBC News reported.

The challenge was to make the difficult judgments on the small numbers amongst them who are going to turn to violence.

Out of 27 terrorist plots disrupted in the last four years, eight have involved right-wing extremists.

The Manchester bombing of 2017 prompted public criticism that MI5 should have done more to stop it, BBC reported.

There have been sweeping changes but the hardest thing for anyone in MI5 is that “we cannot stop every single attack,” McCallum said.

According to The Guardian, McCallum also pledged the domestic intelligence service would boost its diversity and said the Black Lives Matter movement had prompted “really deep and searching conversations with our own people.”

As for dealing with China, McCallum said it requires a complicated balance, citing a need to work with China on major issues, but at the same time being robust in confronting its covert activity, BBC reported.

McCallum, who spent years running covert informants and later led investigative teams before the 2012 London Olympics, used a meteorological analogy, saying Russia was like bad weather but China was a far greater challenge in the long-term and more like climate change.

 He advised that the UK needed to proceed carefully on China because of the economic impact of total disengagement, The Guardian reported.

Britain needed “a broad conversation across government and, crucially, beyond, to reach wise judgments around how the UK interacts with China on both opportunities and risks,” he said.

On the positive side, MI5 also regularly compares notes with its counterparts in the FBI, European agencies and the other nations in the Five Eyes grouping — US, Canada, Australia and New Zealand.

And new legislation is expected to make a big difference in bringing the law up to date in criminalizing what foreign espionage agents get up to inside Britain.