As soon as we read claims that Harvey Proctor had tried to cut off a teenager’s penis but that Edward Heath had stopped him, we knew that they were lies.  We said that they were lies.  And we added that they would be proved to be lies.  So it has come to pass.

We knew they were lies for the simple reason that, as anyone who knew the two men can confirm, Heath and Proctor were incapable of co-operating on anything, let alone such an act: they hated each other.

The policemen investigating the allegations won’t have been experts in Conservative Party history.  But they were capable of interviewing the wife of “Nick” – Carl Beech – who himself invented the claims; of quizzing witnesses in a timely way; if checking to see whether children that Beech claimed had been murdered were none the less still alive.

They did none of these things: indeed, an inquiry into “Operation Midland”, the police investigation into Beech’s claims, found no fewer 43 separate mistakes by the Metropolitan Police.  Yet Detective Superintendent Kenny McDonald declared that he and other “experienced officers from the child abuse team” believed that “what Nick is saying is credible and true”.

Who were these “experienced officers”?  Are they still members of the force’s “child abuse team”?  How can the taxpayer, or anyone else, have confidence in them?  This is a dire week for our institutions.  First, though not for the first time, the Electoral Commission.  Now, and not for the first time either, the Met.

But the force can at least claim not to have been aware of the political background.  The same cannot be true of Tom Watson.  Two years earlier, he had told the Commons that he had “clear intelligence suggesting a powerful paedophile network linked to parliament and No.10”.  Where is the evidence for this claim?

Why did he later declare that Beech “not delusional”, after only one brief meeting with him?  Who was the “survivor” of child abuse who he quoted, saying that Leon Brittan was “as close to evil as a human being could get”?  Was it Beech?  On what basis did Watson urge the police to “continue their investigations”?

None, it seems – since he had little option eventually, while giving evidence to a Select Committee, but to “regret” the description of Brittan.  Readers will spot at once that this form of words is not an apology.  It would clearly be futile to ask for one.  But there are three lessons from this shaming episode, or should be.

First, that it is not, repeat not, always right to “believe the victim” – precisely because, as in this case, the victim is sometimes not a victim at all.

Second, that the damage inflicted on Proctor, Brittan and his family and Field Marshall Lord Bramall – reputational and psychological – cannot, by its nature, be measured.  But what is certain is that Proctor and Bramall will be marked by Beech’s lies for the rest of their lives.

Finally, Watson will doubtless continue to flourish.  But most Labour MPs – and this Conservative site has no hesitation in saying it – are knowing and acute.  They will have clocked the Beech scandal, and Watson’s part in it.  His room for manoeuvre, as the internal push against Jeremy Corbyn goes on, will be just a bit more cramped than it was before.