Some charges against Ken McCallum can be tested, not assumed. Five episodes stand out.

The “ungoverned spaces” (2016–2019). MI5’s compliance team found in January 2016 that data might be held in “ungoverned spaces”. The then-commissioner, Lord Justice Fulford, found the handling “undoubtedly unlawful” and accused officials of “misleading euphemism”. McCallum was deputy director general (DG) from April 2017, and Fulford’s questions focused on what “four of MI5’s Directors” knew in October 2017 and the board knew in January 2018. The apology came from his predecessor, Andrew Parker. A June 2019 review found “a sustained organisational failure”, not “individual negligence or a deliberate intention to mislead”, and asked that the fix be led by the deputy director general personally: McCallum. No published document seen for this article names him among those who knew.

The bulk data judgement. Often dated to 2022, the tribunal’s ruling came on 30 January 2023. It found that MI5 had held data unlawfully from late 2014 to April 2019, did not tell the commissioner until February 2019, and breached its duty of candour in earlier litigation. These are findings against the institution, not against McCallum by name, though he was deputy DG from April 2017.

Manchester Arena bombing (2023). Sir John Saunders said MI5’s “corporate position” at times looked like “retrospective justification” and rejected MI5’s claim that two pieces of intelligence concerning Salman Abedi related to “non-terrorist criminality”. Abedi had been among those encouraged by both MI5 and MI6 to travel to Libya in 2011. McCallum, who as deputy had led the 2017 post-attack review, apologised. The criticism targeted MI5’s corporate account, not him.

Agent X (2020–2026). This case sits wholly in his tenure: the disclosure (2020), the false evidence (2022) and the “robust” assurances to inspectors (2023). But the December 2023 reply to the inspectors was signed by the senior officer in MI5’s oversight engagement team, not by him. He “personally informed” Leveson and apologised in December 2024, and repeated a “full and unreserved apology” to the courts. Yet the review by Sir Jonathan Jones that he commissioned with Yvette Cooper was rejected by the court, its terms of reference “fundamentally incoherent”. Goldring is pointed about one decision that was McCallum’s own. In February 2025, he chose to keep up “neither confirm nor deny”, a position the court called “patently unrealistic”, and accepted that it was “his decision for which he took full responsibility”. Goldring adds that the internal inquiry and the Jones review together “did not amount to an independent review”, but also that “the DG wished to get to the truth”.

Kenova (2024–2025). MI5 found further Stakeknife files in April 2024, after prosecution decisions had been taken. The final Operation Kenova report called this “a serious organisational failure”, one of several incidents “capable of being negatively construed” as attempts to “conceal the truth”. It found MI5 was “closely involved” with Freddie Scappaticci, where MI5 had called its role “peripheral”. McCallum apologised again. The review MI5 requested found that nothing was “deliberately withheld”. Kevin Winters of KRW Law, for bereaved families, called it a “damp squib”.

The case does not belong on this list. The coroner criticised state agencies’ disclosure failings, in a case where, in 1997, Sean Brown was abducted, assaulted and murdered. In February 2024, however, an investigation “indicated that a number of individuals linked to the murder were agents of the state.” At the time McCallum was an agent handler in the north of Ireland for MI5 (fresh out of university). The Secretary of State for Northern Ireland’s refusal to hold a public inquiry was found unlawful by the court, and that ruling was subsequently upheld on appeal. It is now before the Supreme Court. The judgement in this was ministerial, and no finding on MI5’s candour specifically has been made there. One wonders, however, what advice ministers received from McCallum and MI5 in that instance.