Donald Trump with, from left, Arron Banks, Nigel Farage and Andy Wigmore at Trump Tower in November. Banks and Wigmore met the Russian ambassador three days later WIGMORE/FINN/ SPLASH NEWS

The hidden scale of Kremlin links to the biggest donor to the Brexit campaign are revealed today.

Arron Banks, the millionaire businessman who helped fund Brexit, was offered a business deal involving six Russian goldmines.

He also had undisclosed meetings with the Russian ambassador to Britain — set up by a suspected Russian spy — and paid a previously unknown visit to Moscow at the height of the campaign.

The revelations raise explosive questions about attempts by Moscow to influence the referendum result. This morning David Lidington, Theresa May’s second-in-command, called for an investigation.

Emails by Banks and his sidekick, Andy Wigmore, shown to The Sunday Times, reveal the men made repeated contact with Russian officials to discuss business opportunities and issues of mutual interest…