‘Find Christopher Wylie.” That instruction – 13 months ago – came from the very first ex-Cambridge Analytica employee I met. He was unequivocal. Wylie would have answers to the two questions that were troubling me most. He could tell me about Facebook. And he would know about Canada.

What Christopher Wylie knows about Facebook, the world now knows. Facebook certainly knows – its market value is down $100bn. But the Canadian connection remains more elusive. What it is. Why it matters. And why it triggered my search for Wylie.

We heard from him at a session of the digital, culture, media and sport (DCMS) select committee that the BBC parliamentary correspondent Mark D’Arcy described as “by a distance, the most astounding thing I’ve seen in parliament”. Perhaps not because of Wylie’s arresting appearance – though there was that too, his pink hair offset with a suit for the occasion – but because of what he said: a four-hour account of his involvement with Cambridge Analytica that he backed up with documents, a selection of which the committee published two days later.

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It was a moment that marked a significant milestone in our coverage of this story. Because back on 13 May 2017 we received a letter from Squire Patton Boggs, lawyers for Cambridge Analytica, that set out their intention to issue a “pre-action protocol for defamation” – though its immediate concern was regarding an “article that is proposed to be published this weekend”.

Seven fraught hours later, we published an article headlined “Follow the data” . It was centred on one particular document. A document that linked Cambridge Analytica to a small, seemingly inconsequential firm based above an optician’s shop in Victoria, Canada. A document that was among the stash of those released by the DCMS committee on Thursday.

The firm – AggregateIQ – didn’t appear inconsequential. In the words of Vote Leave’s campaign manager, Dominic Cummings, it played a crucial role in the Brexit campaign. For more than a year, a quote from Cummings – “we couldn’t have done it without them” – was emblazoned across AIQ’s website. Words that disappeared from the website a week ago, removed after we submitted our questions to the firm.

The first major article I wrote about Cambridge Analytica last February outlined a relationship between Nigel Farage’s Leave.EU campaign and Cambridge Analytica and the relationships with Robert Mercer, the firm’s main investor, and its shareholder and vice-president Steve Bannon. It kicked off an investigation by the Electoral Commission and the Information Commissioner’s Office. Then, a few days later, a reader from Canada got in touch. Did I know that the telephone number and address listed on Cambridge Analytica’s website as its Canadian office – SCL Canada – belonged to Zackary Massingham? Did I know that he was the chief executive of a company called AggregateIQ? A firm that had worked for Vote Leave? I didn’t.

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Because Vote Leave was the official campaign. It was of a different order of importance to Farage’s Leave.EU. Vote Leave had been recognised by the Electoral Commission. It had been entrusted with taxpayers’ money. It was headed by Boris Johnson and Michael Gove – now both ministers in Theresa May’s government. And who are now seeing the scandal currently engulfing Cambridge Analytica arriving at their doorstep.

Last week we published the account of another whistleblower, Shahmir Sanni, and how he believed that Vote Leave senior officials took advantage of him and his friend, Darren Grimes, to ramp up their own spending. Vote Leave gave their campaign, BeLeave, £625,000 – but in November the Electoral Commission opened an investigation into it. The donation was legal only if BeLeave really was an independent organisation, operating separately. And Sanni had startling new evidence: he said it wasn’t. Sanni – the treasurer – wasn’t even allowed to get his train tickets refunded. Instead, the money was paid directly to AggregateIQ – the company that a year earlier I had found listed on Cambridge Analytica’s website as SCL Canada.

Play Video 10:25 The Brexit whistleblower: 'Not cheating is the core of what it means to be British' – video

The documents published last week finally make the legal connection between AggregateIQ and Cambridge Analytica public. The committee has published an intellectual property agreement between AIQ and SCL Elections – Cambridge Analytica’s parent company. There’s also a service agreement between the two firms that set out revenue-sharing clauses and payment details, an internal Cambridge Analytica staff list that names Massingham, and emails about work the two firms did together for John Bolton, the newly appointed national security adviser to Donald Trump. On 21 August 2014, Alex Tayler, the acting managing director for Cambridge Analytica, wrote to Jeff Silvester, co-founder of AggregateIQ, and said: “Personality Cluster information for the target voter segments for all 3 states (modelled for all voters of interest, not just Kogan sample/seeders).”

“Kogan” is Aleksandr Kogan, the Cambridge University psychologist that Cambridge Analytica contracted to harvest Facebook data. And the “sample/seeders” are the individuals who Kogan’s company, GSR, paid to fill in personality surveys and allow access to their friends’ data.

Last week, AIQ sent us a legal letter. It said that AggregateIQ is not a direct part and/or the Canadian branch of Cambridge Analytica and that it has not been involved in the exploitation of Facebook data or otherwise been involved in any of the allegations of wrongdoing made against Cambridge Analytica. It did not secretly and unethically coordinate with Cambridge Analytica on the EU referendum. It did not share technology with Cambridge Analytica. It never represented itself as SCL Canada. The first it knew of its phone number being on the website was when the Observer reported it. And it is 100% Canadian-owned.

But Wylie told MPs that he had helped set up both Cambridge Analytica and AggregateIQ and that it was based in Canada, in his hometown of Victoria, because Silvester and Massingham, the directors, were friends. From Hansard: “They had new families, had just got a house, and it is not easy to just get up and move to a different country when you have young kids.

Facebook Twitter Pinterest Screengrab taken from AIQ’s homepage.The words disappeared from the site a week ago. Photograph: AggregateIQ

“The compromise was that a Canadian company would be set up … But the deal was that they would sign an intellectual property licence whereby all of the work that they were doing for the company would be assigned to SCL Group and they would trade as SCL Canada, but they set up a Canadian entity, and the legal name was AggregateIQ.”

Play Video 2:55 Cambridge Analytica whistleblower: Vote Leave 'cheating' may have swayed Brexit referendum – video

The same week, Gizmodo, a specialist tech site, published an article headlined “AggregateIQ created Cambridge Analytica’s Election Software and Here’s the Proof” based on research that a cybersecurity firm, UpGuard, had produced. Chris Vickery, the director of cyber-risk research at UpGuard, claimed they had found a repository of code that AggregateIQ left exposed online. The code suggested that it was AggregateIQ that had developed the Ripon platform – the software product that is the foundation of Cambridge Analytica’s technology.

This was part one of the AggregateIQ Files. The second part, which UpGuard published on Thursday, revealed code that suggested that AIQ had built websites and landing pages for Vote Leave, Veterans for Britain, the DUP, Change Britain and Gove 2016. These were all new claims. Last May, David Banks of Veterans for Britain told me it had engaged AIQ in the last weeks of the campaign after it had received a donation from Vote Leave, which it used for digital marketing. For Facebook ads. There was no mention of a website and the AIQ invoice for £100,000 it submitted to the Electoral Commission is for a “digital ad campaign”. The Observer could not reach Banks for comment.

The repository also appears to include code for landing pages for the DUP’s website. The AIQ invoice it submitted to the Electoral Commission, for £32,750.73, is for digital advertising, and a spokesman for Jeffrey Donaldson MP, whose name is on it, told the Observer: “AIQ did not build any pages for the DUP website at any point.”

Another of the sites in the repository appears to be for a campaign not previously associated with AIQ. Change Britain was a “grassroots campaign” with “1000s of volunteers who want to help make Brexit happen” led by Gisela Stuart, formerly Labour MP for Birmingham Edgbaston and the chair of Vote Leave. Its code appears to contain details of a Vote Leave staff member’s email address. Stuart did not respond to questions about who had paid for or commissioned this site.

Revealed: Brexit insider claims Vote Leave team may have breached spending limits Read more

The final discovery in UpGuard’s AIQ find is code for a website for Gove 2016. This was the campaign Gove launched on 30 June, six days after the referendum result, to be leader of the Tory party. AIQ gained administrator access to the site the same day Gove turned on leadership candidate Boris Johnson and announced his own intention to run. When asked about the work AIQ did for Gove, a spokesman said: “The Gove 2016 campaign paid AIQ £2,720.46 in July to set up its website. The payment was authorised by the campaign manager and paid for from funds donated to the campaign. All campaign spending was fully declared to CCHQ as required under Conservative party leadership election rules.”

AIQ did not respond to inquiries about its work on the Gove 2016, Change Britain, DUP and Veterans for Britain websites, or the UpGuard report.

Gove’s statement above wasn’t just given to the Observer, however. It found its way to the rightwing gossip site Guido Fawkes two days ago, in an apparent spoiler for this story.

It’s not a good look. But then, of the many questions being asked by the British authorities investigating Vote Leave – the Electoral Commission and the Information Commissioner’s Office – one must be: what did Gove know?

Sanni, the whistleblower who came forward last week to tell his story about the BeLeave donation, claims Gove knew everything. “Everyone associated with the campaign knew who Darren was,” he says. “Everybody congratulated us and knew what role we’d played. Michael Gove knew exactly how important we’d been. He’s a close friend of Dom Cummings. Of course he knew. Boris Johnson knew. Everybody knew.”

Facebook Twitter Pinterest The building housing Cambridge Analytica’s office in central London. Photograph: Hannah Mckay/Reuters

Cummings, the campaign mastermind behind Vote Leave, had worked as a special adviser to Gove when he was in the Department for Education. His fellow adviser was Henry de Zoete, the head of Vote Leave’s digital operations. This is a tight-knit group who have known each other for years. “The thing about Gove and Cummings is that they are friends,” says Sanni. “They hang out at each other’s houses. It’s a relationship that goes well beyond being colleagues.”

It was Cummings’s name – along with de Zoete’s – that was deleted from 140 files on a Google shared drive two weeks after the Electoral Commission opened an investigation last March. A drive that was set up by Vote Leave to share content with BeLeave and AIQ. Vote Leave says it acted “ethically, responsibly and legally in deleting any data”. Last week Cummings said of Sanni and Wylie: “I think they have lied to the Observer and its lawyers”.

But it is Gove, the co-convener of the campaign, along with Stuart, its chair, and Johnson, its figurehead, who need now to answer questions. It’s the proximity of Vote Leave’s activities to the heart of government that is the most troubling aspect of this. Gove and Johnson are Theresa May’s ministers. Two other Vote Leave directors implicated, Stephen Parkinson and Cleo Watson, are advisers to May. Watson said: “I absolutely deny the claims being levelled against me.” Parkinson said the allegations were “factually incorrect and misleading”.

Campaigns are forbidden by law from coordinating. Unless they declare spending jointly. None of these campaigns did. They were all separate. They were all separate – and all connected to AggregateIQ. Facebook would know, of course, if there was a common plan. But Facebook is a black unknowable box. And Mark Zuckerberg has, for the third time, turned down parliament’s request to answer questions on that and other issues.

A year ago, I was told that Christopher Wylie was the key to understanding AggregateIQ. To unravelling Cambridge Analytica’s Canadian connection. Last week, the week that marked the one-year countdown to Britain exiting the EU he told parliament about it in explicit detail. Now it is up to parliament. It is in possession of Cambridge Analytica’s and AIQ’s corporate documents. It supports a government that is intimately entwined in this. And how it negotiates those two irreconcilable facts may be a yardstick that future generations will come to measure it by.

• This article was amended on 3 April 2018 to remove an incorrect reference to the Gove 2016 website having never gone live. It was online during Michael Gove’s bid for the leadership of the Conservative Party in early July 2016.

