Urmstongran You haven't any idea whether he has a leg to stand on. You don't know what evidence he has. I don't know, and neither do you, what grounds he'll cite for constructive dismissal. It's actually very hard to prove. Rutnam isn't stupid, so he must have something serious.
All civil servants are bound by a code of practice, which includes confidentiality, so the public does not know the truth of what's been going on. Interestingly, Amelia Gentleman, Boris Johnson's sister-in-law and the journalist who broke the Windrush scandal, has asked via Twitter for Rutnam to contact her.
It's all a bit peculiar.
1) His employer is actually the Civil Service, not the government.
2) The maximum payout for unfair dismissal is around £85,000 and I would bet anything he was offered more than that to go quietly. Brodie Clark, the former head of UK Border Force, was paid over £200k by the Home Office to go.
An employment tribunal might not even accept the case, if he has already refused a payout higher than that which the tribunal could award.