I learned fairly early on my journalistic career that getting senior police officers to take responsibility for their actions is no easy task. In the early 1980s, the then Chief Constable of Derbyshire, Alf Parrish, was allowed to retire on a full police pension despite having spent £32,000 of ratepayers' money building an electronic partition in his office which slid back to reveal a space for private cocktail parties.
In another episode, about which I would love to be able to say more, a deputy chief constable's administrative error resulted in police officers being paid so much overtime it practically bankrupted the force concerned. Once again, despite attempts by the local police authority to bring him to account, the man concerned was allowed to retire on a full pension, and his misdemeanours were never actually made public.
So it doesn't greatly surprise me that Sir Ian Blair clearly views the de Menezes case less as a question about whether anyone should be seen to take responsibility for the tragic death of an innocent man and the systemic failures in the Metropolitan Police which led to it, and more about the much more important issue of principle of whether he should be allowed to keep his job.
It's frankly beyond belief that he hasn't quit already, but he is clearly not on the same planet as most of the rest of us. It's almost as if he sees the case as just part of a much bigger battle between the forces of conservatism and the forces of liberalism, a battle in which he sees himself as being on the side of the angels.
If so, it explains why all of the support for Sir Ian remaining in his job is coming from the political left. While the right and centre are at one in their calls for him to go, the Labour establishment, from Home Secretary Jacqui Smith to London Mayor Ken Livingstone, is adamant he should not.
I am as convinced as I can be that this is less down to the merits of the case and more down to tribal loyalties. Sir Ian is seen as "Labour's man," and more generally as a force for "modernisation" and "reform" in a force that, not so long ago, was found to be institutionally racist. Therefore he must not be allowed to be forced out by those nasty reactionary elements.
To base one's view on the internal political ramifications for the Met, however, or even on the ramifications for policing in London, is to lose sight of a much more important issue of principle - the fact that restoring trust in public life requires that those at the top start taking responsiblity for their actions.
Sir Ian Blair's removal - and in my view it's a matter of when, not if - may well result in him being replaced by a more conservative figure - a "copper's copper" as they are known in the shorthand. But if that helps restore a culture of accountability to our public life, it will ultimately be a larger victory for the liberal-left.
An edited version of this post appears on Liberal Conspiracy.