The Home Secretary, Theresa May, faces fresh embarrassment over the borders fiasco after being told by her lawyers that the civil servant at the centre of the storm will win his constructive dismissal case against the department.
Their conclusion means Brodie Clark, who earned £130,000 a year as head of the UK Border Force, is likely to receive a hefty pay-off reflecting his 40 years of public sector service.
He and two colleagues were suspended last week after revelations that biometric and anti-terrorism checks were secretly eased over the summer at ports.
Ms May pinned the blame squarely on him, insisting she knew nothing about the decision. Mr Clark quit on Tuesday, complaining that he had faced such a campaign of vilification that he could not get a fair hearing.
Accusing Ms May of making misleading remarks about him, he said he was resigning to launch a constructive dismissal case.
The Home Secretary's lawyers advised her Mr Clark looks certain to win as the public comments – and private briefing – about him broke Whitehall rules on handling disciplinary action.
The hostile briefing against Mr Clark dismayed colleagues within the Home Office and other departments.
One Downing Street insider told i: "It was an aggressive operation that backfired." Mr Clark was described by Home Office sources as a "rogue civil servant" and it was suggested he could even be prosecuted. His union, the First Division Association, said Ms May had spent two days "traducing him and damning him".
Alan Johnson, the former Labour home secretary, told MPs: "The treatment of Brodie Clark, who I know and respect and admire, has been reprehensible."
Mr Clark had maintained his silence until he resigned and is now preparing to set out his case when he appears before MPs next Tuesday.