German chancellor Friedrich Merz presents US president Donald Trump with the framed birth certificate of Trump's grandfather, in the White House on Thursday. Photograph: Brendan Smialowski/AFP/Getty Donald Trump cherishes his German heritage so much that, for years, he claimed his father’s roots were in Sweden. That was a big personal reason – ahead of Ukraine or trade uncertainty – why Friedrich Merz was on high alert for his inaugural visit with the US president in the Oval Office. And that is why he ramped up the personal, and dispelled those Sweden rumours for good, by presenting the president with the...