As Nato’s secretary general, Jens Stoltenberg, and the UK prime minister, Rishi Sunak, visit Warsaw, we examine the role that Poland plays in the diplomatic field. Then: Donald Trump’s criminal trial; Taiwan wants to remove statues of Chinese dictator Chiang Kai-shek; and an exploration of the future of ticket resale with the managing director of Viagogo. Plus: aviation news and a lost Klimt painting is auctioned.