Newly revealed video footage shows former Donald Trump campaign manager Steve Bannon in London discussing his ties with Boris Johnson.

The Tory leadership frontrunner has previously dismissed the idea of an association with the controversial US strategist – who has been trying to build a movement of right-wing populists in Europe after leaving the White House – as “a lefty delusion”.

Yet previously unseen documentary footage from July 2018 shows Mr Bannon talking about his contacts with Mr Johnson and explaining how he helped shape the Conservative politician’s resignation speech, in which he stepped down as foreign secretary over the government’s Brexit plan.

“I’ve been talking to him all weekend about this speech. We went back and forth over the text,” Mr Bannon is heard saying as he reads a copy of The Daily Telegraph.

Asked how he had contacted Mr Johnson, the US strategist replied: “Talked to him initially over the phone then it’s just easier to go back and forth on text. It’s just easier. I’ve been telling him one of my recommendations is that he gave one of the most important political speeches of 2016.”

“[It] was his closing speech, a three-to-five-minute speech in June 2016, his closing argument on national TV for the Leave campaign,” he added.

“And all I was telling him all weekend was just to incorporate those themes. Those same themes. Basically, he was saying that June 23 was independence day for Great Britain. Their independence day being like our July 4.”

The video, obtained by The Observer, was filmed by US filmmaker Alison Klayman for a forthcoming documentary, called The Brink, about Mr Bannon. The trailer for the documentary shows Brexit Party leader Nigel Farage in discussion with Mr Bannon.

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The new clip shows the US strategist praising Mr Johnson’s book about Churchill and divulging how he established a relationship with the Tory figure shortly after Mr Trump’s presidential victory.

“Right after we won Boris flew over. Because their victory was as unexpected as ours. I got to know him quite well in the transition period,” he said.

Mr Johnson’s team played down the contact. A spokesperson said: “Any suggestion that Boris is colluding with or taking advice from Mr Bannon or Nigel Farage is totally preposterous to the point of conspiracy.”

Earlier this year The Independent revealed the links between Mr Bannon’s fledging training academy for right-wing populists, based in Italy, and Tory political figures in the UK.

The Academy for the Judeo-Christian West’s day to day operations are handled by a right-wing think tank called the Dignitatis Humanae Institute (DHI). Benjamin Harnwell set up the DHI while working for Tory MEP Nirj Deva at the European parliament, before leaving that role to focus on the institute.