Donald Trump allegedly discussed potentially sensitive information about US nuclear submarines with an Australian billionaire three months after leaving office, according to an American media report. These allegations, which Trump denies, have raised further questions about his alleged handling of classified information – already the subject of separate and unrelated criminal charges in the US.Guardian Australia’s foreign affairs and defence correspondent, Daniel Hurst, discusses why an Australian businessman and multiple former prime ministers are facing questions over this story and how these allegations could affect future Australia-US relations