THE CAMBRIDGE RING:

In August, Sam Patten, a US political consultant who had worked for Cambridge Analytica on campaigns in the US and abroad, struck a plea deal with Mueller after admitting he had failed to register as a foreign agent for a Ukrainian oligarch.

He became a subject of the special counsel's inquiry because of work done with Paul Manafort, Trump's campaign manager, in Ukraine. He had also set up a business with Konstantin Kilimnik, a key figure who Mueller has alleged has ties to Russian intelligence and who is facing charges of obstruction of justice. In a 2017 statement to the Washington Post, Kilimnik denied any connection to intelligence services. Kaiser, however, is the first person connected directly to both the Brexit and Trump campaigns known to have been questioned by Mueller.

The news came to light in a new Netflix documentary, The Great Hack, which premiered at the Sundance film festival last month and is expected to be released later this spring. Film-makers followed Kaiser for months after she approached the Guardian, including moments after she received the subpoena. She claims the summons came after the Guardian revealed she had visited WikiLeaks founder Julian Assange while still a Cambridge Analytica employee in February 2017, three months after the US election.

One part of Mueller's investigation focuses on whether the Trump campaign sought to influence the timing of the release of emails by WikiLeaks before the election. Investigators are looking at communications between them. In the film, Kaiser says that she has gone from being a cooperating witness to a subject of investigation because of her contact with Assange.

In October 2017, it was revealed that Alexander Nix, the chief executive of Cambridge Analytica, had contacted Assange in August 2016 to try to obtain emails from Hillary Clinton's presidential campaign - which indictments from Mueller's team say were obtained by Russian military intelligence - to use in Donald Trump's campaign. When Kaiser gave evidence to parliament last year, she was asked about her relationship with Assange and WikiLeaks but failed to reveal that she had met Assange.

In the documentary, Kaiser is shown after receiving an email from the Guardian last June asking about meeting Assange and alleged donations of cryptocurrency to WikiLeaks. Kaiser did not respond to the email at the time, but on camera says: "She knows I met Assange. And she knows I donated money to WikiLeaks in bitcoin."

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