After an election campaign built on attacking the reputation of his rival’s son, Donald Trump is facing calls for a new legal investigation into his activities in Ukraine where he and his associates were looking for dirt on Hunter Biden.

The Stories of our Times podcast has spoken to a Ukrainian businessman who has admitted, for the first time, that he was asked to lie about Hunter Biden’s business dealings to damage Joe Biden’s reputation. In return, he was promised a US visa and legal immunity.

These allegations raise fresh questions about a story that has dogged the Trump administration, leading to a Senate inquiry and the impeachment of Mr Trump.