Donald Trump’s relationship with Deutsche Bank has lasted longer than any of his marriages and is cloaked in more secrecy.

Now the US Supreme Court is considering whether to shed light on the links between the American president and Germany’s largest bank. Manhattan prosecutors and Washington lawmakers want tax and financial records related to Mr Trump, his family and businesses. Mr Trump has sued to block them.

When the justices rule in the next few weeks, there will be understandable interest in the window this might provide into Mr Trump’s finances. Americans are still waiting to see the president’s tax returns, years after he promised to make them public. In the absence of hard data, speculation swirls: is Mr Trump really a billionaire? Are his business dealings above board?