It presented Sir Keir Starmer with his first big challenge in office, and the Southport stabbings – followed by riots – look set to colour the early stages of his premiership.
He dealt with the immediate aftermath by successfully mobilising the justice system and fast-tracking offenders through it – a throwback to his days as head of the Crown Prosecution Service (CPS).
But the longer-term problem this horrendous crime poses will take him very far from his comfort zone.
On Tuesday, he tackled the failures of public institutions in dealing with what was a known threat from Axel Rudakubana, who was referred to the anti-terror body Prevent three times.
More pernicious though are the baseless but corrosive accusations of a cover-up which started online and have high-profile champions in the Commons, with Nigel Farage and Robert Jenrick repeating the conspiracy theories.
This represents the new frontier of British politics, in which misinformation has become mainstream and threatens to destabilise our political system from the inside.
It was a surprisingly bold approach from the prime minister in response to the Southport stabbings.
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In this speech, he took head-on a justice system that has been under pressure over the way it responded to the incident.
At the centre was the promise of a wide-ranging inquiry, in which “nothing is off the table” and the assurance that things will change, including, if necessary, the law.
It was all designed to take back the narrative, and to present himself not just as a dedicated upholder of the law but someone who is prepared to radically reform it too.
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The toxicity of online accusations of a cover-up was on full display in the Downing Street news conference as questions focused on the suggestion the prime minister “withheld information”.
This is a long-established part of the UK’s justice process and is designed to prevent a trial collapsing, and yet the idea that Sir Keir Starmer should have spoken out has taken hold.
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His history as a lawyer and director of public prosecutions put him on a firm footing in defending the legalities of his response, but the barrage of questions suggests this could still damage the public’s perception of him.
Taking on the tough issues that have arisen in the aftermath of the Southport stabbings was the theme of Sir Keir Starmer’s speech on Tuesday, and it delivered on concrete announcements.
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Central to the response was an inquiry which he said would “leave no stone unturned” in laying bare the failures of multiple institutions, which identified Rudakubana as a threat but didn’t act.
But the threat to Sir Keir Starmer’s reputation over his response clearly remains, with online conspiracy theories thrust into the spotlight during the news conference.
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Question after question addressed the lack of information released into the public domain about the killer by the prime minister.
Such an intervention would have been unprecedented and compromised the legal process, and he set out his case clearly.
But if this is the narrative that takes hold, overshadowing the broader response, it could be corrosive to his fledgling government.
