Allow me to introduce Dominic Slack-Oxley. Never heard of him, I hear you cry. Oh but you have. You hear from him every time you pick up a newspaper or turn on the TV news. Slack-Oxley is everywhere. More than Facebook or Vladimir Putin, he is the most reliable source of fake news in Britain.

When you read about ‘Downing Street sources’ saying with absolute authority that Boris Johnson would never send a letter to Brussels to extend the Article 50 deadline, only for him to do just that, Slack-Oxley is to blame. When political correspondents boast of their exclusive access to ‘Number 10 sources,’ ‘Government sources’ and the ‘Prime Minister’s official spokesman,’ they mean Dominic Slack-Oxley is using them to push out the latest propaganda line.

Like many fantastical fictions, Dominic Slack-Oxley is not one man but many. A part of him is Robert Oxley, Boris Johnson’s press secretary, and a former spin-doctor for Vote Leave. Here is how he operates. On 24 August, the Observer revealed that Johnson was considering closing Parliament to avoid scrutiny of his Brexit plans. Oxley told political correspondents attending the G7 summit the story could not be more wrong. They dutifully reported a ‘government spokesman’ as saying the ‘claim that the government is considering proroguing Parliament in September in order to stop MPs debating Brexit is entirely false.’

I phoned those correspondents up and they told me that Oxley was the ‘government spokesman’ in question. I passed the information on to Observer readers, and it was not denied. A few days later Jacob Rees-Mogg persuaded the Queen to suspend Parliament on Johnson’s behalf.

When you hear 'the Prime Minister’s official spokesman’ promise that X will happen, only for Y to happen within hours of his announcement, you are usually hearing the voice of the unimprovably-named James Slack. Any sensible Conservative politician would run a mile from him. While he was working at the Daily Mail, he wrote the copy for its ‘Enemies of the People’ attack on the judiciary of November 2016, before being appointed as the Prime Minister's Official Spokesperson by Theresa May. Nothing did more to radicalise liberal opinion and turn moderate conservatives against the Brexit right. As a result, most people on my side of the argument believe Brexit is no longer just a fight about membership of the European Union but a defence of the British constitution against its enemies. But then Johnson has to appeal to the portion of the electorate lost in raging conspiracy theories about the ‘Remainer elite’ and I suppose it isn’t a surprise that he didn’t sack Slack or cut out the Slack, but kept him in the job instead.

Behind them both lies Dominic Cummings. The Downing Street press operation fears him as a loose cannon but dares not contradict him. I suppose it is to the credit of Westminster journalists that they actually acknowledge Cummings exists. And for this chink of transparency – this one glimmer of light amid the murk – their readers and viewers are doubtlessly grateful. I doubt, however, if one reader or viewer in a 100,000 knows the names of Oxley or Slack.

And that’s just the way Dominic Slack-Oxley likes it. By extending the protections afforded to whistleblowers (whose jobs would be at risk if they were identified) to official government spokesmen who take no risks and whose actual job, paid for by the taxpayer, is to speak out for their employer, journalists create a propagandist's paradise.

Paragraph 14 of the Special Advisers Code of Conduct says: ‘Special advisers must not take public part in political controversy... They must observe discretion’ and ‘express comment with moderation’. It accepts that special advisers charged with dealing with the press are allowed ‘a degree of political commitment’. However, ‘briefing on purely party political matters must be handled by the Party machine’.

It forgets to note that, as long as journalists are the eager conduits for unattributed spin, the code is unenforceable.

Here are two newspaper stories that make the point for me. The first appeared in the Mail on Sunday at the end of September. Number 10 ‘sources’ claimed Remain MPs were engaged in 'foreign collusion' with the French government and the EU in a ‘plot to allow John Bercow to send a “surrender letter” to Brussels asking for a delay to Brexit’. The second story should have appeared but didn’t. It reported that Oxley, Slack or Cummings or a Dominic Slack-Oxley combination of the above ‘claimed’ that a plot was afoot.

Between the two stories lies the difference between a free press and a courtier press. Openness allows politicians and their sidekicks to be held to account when the story is revealed to be ‘party political’ garbage. It was always likely that it would in this case. The Mail on Sunday piece even admitted that ‘No 10 declined to discuss what evidence they had’. And as a point of fact, Johnson forgot his promise to ‘die in a ditch’ rather than ask for an extension and sent the ‘surrender letter’ himself.

Reform should begin at the editorial level. Reporters would not dare stand up to Downing Street on their own, so editors, particularly editors at the TV stations, must take two steps. They must insist that when the Prime Minister’s official spokesman (or his counterparts in the opposition parties) gives a briefing he must be named – as he is in virtually every other modern democracy. Editors would then have to decide whether to blow the whistle when a ‘Downing Street source’ consistently fed them fake news, or quietly ban their reporters from speaking to him or her again.

You may retort that the pack of Lobby correspondents contains some of the best journalists in the country – and you would be right. You could say that Westminster journalism has always offered the protection of anonymity to ‘sources’ who don’t need it. And you would be right again. The trouble with the Johnson administration is that it has taken existing conventions and pushed them to the point where political correspondents are complicit in disinformation campaigns. In the end, their viewers and readers will lose trust in them. Indeed, many already are. As Robert Harris said recently: ‘the quality of Brexit coverage would be vastly improved if Dominic Cummings was named as the source each time he briefs a journalist. In 40 years I've never seen so much hyperbolic garbage treated as serious news.’

The Lobby has allowed Dominic Slack-Oxley to become Westminster’s equivalent of Macavity the Mystery Cat, who can never be caught or held to account for his crimes. If T.S. Eliot were covering the Brexit debacle, he could update Cats and write:

“ 'Slack-Oxley, Slack-Oxley, there's no one like Slack-Oxley

There never was a cat of such deceitfulness and suavity.

He always has an alibi, and one or two to spare:

At whatever time the deed took place - SLACK-OXLEY

WASN'T THERE!'