Roy Greenslade: Iain Duncan Smith affair shows how vital keeping sources anonymous can be

It is also the only antidote to PR untruths or, less pejoratively, spinning. In the above case of The Times, it was noticeable that the claim by the “cabinet colleague” was disputed by “a senior member of staff at No 10” who was quoted as saying: “The Prime Minister does not believe the Chancellor was responsible for what happened. They are working as closely as they ever have done.”

Note first that one anonymous source was countered by another anonymous source. And second that the No 10 source was issuing a total denial. Although they cannot both be right, it did not stop the editor from publishing because he was assured, presumably, that his two journalists were not guilty of invention.

I have no doubt that there have been occasions when anonymous quotes have been concocted but much more rarely than some critics would believe. The reality is that people — whether they be politicians, police officers, business leaders or, yes, editors themselves — confide in journalists in the expectation that the information will end up being published.

It is true that anonymity allows a source to be malicious. But journalists are, or should be, sceptics. They seek to avoid playing the role of stenographer. Part of their job is to ascertain the motives behind a person telling them things “off the record” or “on an unattributable basis”.

This convention is learned early in journalistic training — not least because British culture at all levels is based, if not on secrecy, then certainly on discretion. I have lost count of the times an interviewee has said, even over a relatively trivial matter: “Not that you got it from me, of course.”

Journalistic codes urge reporters to protect their confidential sources. The one administered by press regulator Ipso says journalists have “a moral obligation” to do so.

There is no obligation not to expose a rival’s source. So, when a really big story breaks, such as the Sun’s “Queen backs Brexit” scoop, an inevitable mole hunt begins. That can be passed off as part of a Fleet Street game.

But it is sobering to reflect that anonymity results in the publication of stories that would otherwise remain hidden. Anonymous sources, for good or ill, are therefore in the public’s interest.