As a senior civil servant, Sue Gray spent decades shrouded in the secrecy of Whitehall officialdom. Now she has hit the headlines again, as an update on the investigation into her proposed move to become Keir Starmer’s chief of staff is published. Who is Sue Gray? Once described as “the most powerful person you’ve never heard of”, Gray spent many years climbing the rungs of the civil service ladder. The two-paragraph summary of her career on the government website is purely perfunctory, and belies the knowledge and experience she has built up in Whitehall since the 1970s. Having worked in the transport, health, and work and pensions departments, her career rocketed when she joined the Cabinet Office’s propriety and ethics team in 2012. Its remit, to look quietly into the behaviour of ministers and civil servants, put Gray at the centre of Whitehall – but she was never a household name. Why did she become one of the most well-known civil servants? Gray faced intense public scrutiny when she took over the job of investigating Partygate in December 2021. At the time, she was universally praised by MPs, who believed she would do a thorough and fair job. Her reputation was fearsome. The nearly five-month inquiry shone a light on the extent of partying and lockdown breaching by politicians and officials during the Covid pandemic. While she made no formal recommendations about any sanctions, the extent of rule-breaking in No 10 was partly responsible for Tory MPs deciding to push Boris Johnson out as prime minister. What did she do after the Partygate inquiry? Uncomfortable at having become such a public figure, Gray sought to slide back into relative obscurity. Until she resigned, her official position had been second permanent secretary – the de facto deputy civil servant in charge of running a department – in the Cabinet Office. Her key responsibilities were the constitution and the UK union, and she had remained an influential figure in Whitehall. However, she was reportedly snubbed by the cabinet secretary, Simon Case, for a promotion to permanent secretary. Such a move was viewed by many as integral to eventually succeeding Case, who many believe is likely to be forced out. Gray was said to be frustrated, and looking for another way to potentially catapult herself to the top job – or play a more influential role in government. But it surprised everybody in Westminster when it emerged Labour was preparing to appoint her as Keir Starmer’s new chief of staff. Why did the move stumble? All ministers and senior officials who are preparing to leave their roles must consult the watchdog that is meant to keep an eye on the revolving door of political jobs. Gray’s appointment was subject to approval by the advisory committee on business appointments (Acoba), which can impose conditions and a cooling-off period before future employment can begin. While the Acoba process is still under way, the government has quickly carried out its own internal inquiry into Gray. A Cabinet Office investigation was initially expected to conclude she broke the civil service code by holding talks with Labour about the new role without informing officials. Under the rules that all managers in Whitehall are required to follow, Gray should have declared any meetings she had with opposition figures to the ministers in her departments. But after wrangling between ministers, who wanted to publish critical findings of their inquiry before Acoba reported, and senior civil servants, who were wary about doing so, it seems the latter won. Oliver Dowden, the Cabinet Office minister and deputy prime minister, released a statement saying he was “unable at this stage to provide further information” about Gray’s departure to “maintain confidentiality towards an individual former employee”. He said the government had submitted its own report to Acoba about the restrictions Gray should face, but these would remain confidential. Conservative MPs are keen to capitalise on Gray seeking to work for Labour – and suggest that her personal political motivations may have played a part in her damning report into Partygate. The headache for Labour will be whether to push ahead with hiring her, given the Tory attacks on Starmer for trying to paint himself as “Mr Rules”.