On 6 June, Damian Collins, the Conservative MP for Folkestone and chair of the select committee for digital, culture, media and sport, tweeted a photo he had taken of a bronze bust inside Portcullis House, the office block where much of the Palace of Westminster’s day-to-day work is done. “Jeremy Thorpe makes an appropriate silent witness in the Grimond Room today for our @CommonsCMS select committee hearing with Alexander Nix from Cambridge Analytica #AVeryEnglishScandal,” Collins said.

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It was a reference to the BBC drama in which Hugh Grant played Thorpe, the Liberal leader who, in 1978, faced trial for plotting to murder his lover, Norman Scott. And it was true that what was unfolding that day was another very English scandal. Only, unlike the Thorpe drama, it was one that had global significance.

Alexander Nix, a younger, blonder Hugh – an old Etonian with studied manners and Merchant-Ivory hair – had not been accused of murder and it was not a trial, officially. And yet it was. What the Grimond Room has witnessed over months is the entire structure and machinery and future of our democracy on trial. A trial in which Nix’s witness testimony provided a gripping real-time drama conducted over many hours, in front of the world’s media, with MPs asking questions on subjects that ranged from hiring Israeli intelligence agents to bribing Caribbean politicians to subverting elections in countries over five continents.

These not are subjects usually covered in anonymous committee rooms in Portcullis House. But then these are not subjects that the DCMS committee had any idea it would be covering when it announced an inquiry into fake news in February last year. But week by week, and witness by witness, it has made public an extraordinary and still unfolding story.

There is nothing on this advert to indicate that it was for Vote Leave in any way. In fact, it was a data harvesting operation that Dominic Cummings boasted about on his blog. Photograph: DCMS Committee

It has heard from 61 witnesses, taken more than 150 written submissions and conducted 20 oral evidence sessions, including one in Washington, the first outside parliament. To watch its progress was to watch a true crime box-set happening in real time. I was the only journalist at Nix’s first appearance in February. His second was packed with international press and live-streamed to thousands of people across the world. The 27 March hearing with Christopher Wylie, one week after he broke open Cambridge Analytica’s massive abuse of Facebook data, in the Observer and New York Times, was watched by the biggest audience that parliament has ever had.

When the scandal erupted, it was the DCMS committee that became the unofficial and impromptu investigating authority. The US has special counsel Robert Mueller leading its inquiry into the Donald Trump campaign’s links to Russia. Britain had a cross-party group of 12 MPs: random amateurs with no expert training who stepped up and led an inquiry that has been public, open and asking more and more difficult questions. Crucially, it has refused to take no for an answer.

Today it publishes its first blockbuster 89-page report (another is due in the autumn), and it looks as if the actions of what the Washington Post calls the “plucky little panel” will come to be seen as a watershed moment in the history of Silicon Valley.

Paul-Olivier Dehaye, a Switzerland-based data expert who was one of the witnesses called to give evidence, has fought for years to force Facebook to face up to its legal obligations. He called the report a damning and “comprehensive critique” of all social media companies, but particularly of Facebook. “It looks like the cops are finally arriving.”

The report sets out in great detail what is known about fake news, data targeting, Cambridge Analytica, Facebook and Russian interference, and issues a set of demands that includes new regulation, legislation, codes of ethics and police investigations. It calls for “algorithmic auditing”: for the heavily guarded secrets of the tech companies’ “black boxes” to be smashed open. And for a digital version of Ofcom that would make companies legally liable for harmful or illegal content.

Another of Vote Leave’s “dark ads”. These were finally made public last week when Facebook handed over the material to the DCMS committee. A huge number of them play on fears of Turkey joining the EU. There are no plans for Turkey to join the EU. Photograph: DCMS Committee

Jason Kint, Washington-based chief executive of Digital Content Next, , has become an avid follower of the committee’s work, getting up early to watch the unfolding drama on his computer. He said that parliament had achieved something that US lawmakers had, as yet, failed to do: it had called Facebook to account.

“Lots of people were very disappointed by [chief executive Mark] Zuckerberg’s appearances in Congress and the level of questions he received. They took it as a fait accompli that we couldn’t hold Facebook to account. What I’ve been saying is that if you watch the Commons committee you can see that’s not true. I’ve been impressed, both by the format and the bipartisan approach and how far they’ve come in understanding tech and big data. They are more threatening to Facebook than almost any other body in the world. And that’s why Zuckerberg won’t come and give evidence.

“What I appreciate about the format is that the MPs ask these questions, which sound very innocent in the way they are being asked in this very British style. But they then get to follow them up, and it leads to answers that are quite profound and important.”

The answers have been profound and important. Though the report makes clear that it is some of the answers the committee has not received that have been even more so. There is a golden thread that runs through the 89 pages of this interim report, and that is what Collins calls “Facebook’s complete lack of moral responsibility”. Its complete absence of “moral leadership”. The “disingenuous” responses from its executives. Its determination to “time and again… avoid answering our written and oral questions to the point of obfuscation”.

Collins admits that he and the committee had no idea that they would find themselves in the eye of a global political and media storm. “We stumbled into this world. Fake news suddenly became this gateway into this world that all of a sudden started to tumble down around us.” A world that included not only data harvesting – though that was part of it – but also evidence that Collins describes as “mindblowing” – computer hacking in Nigeria, corruption across the Caribbean and “these really interesting links between Julian Assange and WikiLeaks and Hillary Clinton”.

Here Vote Leave found a way to exploit Jeremy Corbyn’s publicly stated views in support of remaining in Europe to harness support for their own side. Photograph: DCMS Committee

One thing that Collins says has struck him is “just how many connections take you back to Russia. At every step of the way. There’s never been a point where we’ve thought, ‘Oh it’s not as bad as we feared.’ The connections just seem to deepen and become more significant.”

Today he tells the Observer that Britain needs its own Robert Mueller to look into Russian interference. “We know that this happened in America. And we know that the FBI is investigating and is calling on our evidence. We need to know that this is being taken equally seriously in Britain. We need to be satisfied that this is under the scrutiny of our agencies, and at the moment we don’t. We really do need a statement from the government now. We need reassurance of what investigations there are and that this is being properly looked at.”

The report accuses the government of a “disconnect” between the prime minister’s public statements about Russian meddling in elections and planting “fake news” in an attempt to “weaponise information”, and its actions. It says: “It would be wrong for Robert Mueller’s investigation to take the lead about related issues in the UK.”

Facebook, its moral and ethical failings, its refusal to answer questions and take responsibility, are at the centre of the report. But the individual who comes in for the sharpest criticism is Dominic Cummings, Vote Leave’s campaign director. His “contemptuous behaviour is unprecedented in the history of the committee’s inquiries”.

On Friday, it announced that Facebook had finally handed over Vote Leave’s advertisements, after a long and bitter struggle. These were the ads that Cummings had masterminded: “dark ads” previously unseen by anyone other than those who had been anonymously targeted, most of which were served in the critical final days of the campaign, the period Cummings called the campaign’s “Waterloo”. It is an extraordinary and revelatory collection: a collection dominated by overtly racist lies – notably that Turkey’s 76 million citizens were about to join the European Union.

These are what, until now, we have been calling fake news, a term that the committee rejects. This, it says, is “misinformation” or “disinformation”. Vote Leave, by extension, won the referendum by running a disinformation campaign. And Cummings’s refusal to answer questions is an “urgent matter for consideration… by parliament as a whole”.

Cummings retaliated. In classic Cummings fashion. He leaked the report early and smeared the committee as “charlatans”.

The world learned early – through Cummings’s trademark rule-breaking, duplicity and lack of respect for parliament – that Facebook and all of Silicon Valley have been put on notice. Their time of unfettered free-range access over all aspects of our lives is over. And it was also the week in which Facebook finally faced the consequences of the Cambridge Analytica scandal with $120bn knocked off its share price. But it remains to be seen what, if anything, will be Cummings’s Waterloo.

• This article was amended on 31 July 2018 to correct a place name and restore the words “written and oral questions” to a quotation from the DCMS committee’s report.