Scotland Yard risked being dragged into a politically charged row over Sir Kim Darroch’s emails after a teenager working for the Brexit Party said he was the middleman who obtained the classified documents.

Steven Edginton, 19, who runs the Brexit Party’s social media feeds, insisted he passed the documents to the political journalist Isabel Oakeshott.

Mr Edginton, who also describes himself as a freelance journalist, said he did not want his name on the articles, subsequently published in the mail on Sunday, “to avoid possible controversy”.

But the key role of Mr Edginton in the leak will cause problems for the Metropolitan Police and for intelligence agencies in what is already a highly sensitive investigation.