It was formed to unite the world’s strongest countries and preserve peace, but as NATO holds a celebration summit for its 75th anniversary, it faces tricky challenges. Climate change is jeopardising Scottish salmon, one of Britain’s biggest food exports (10:15). And why North Korea is sending hot air balloons over to the South, filled with rubbish and faeces (16:50).

Listen to what matters most, from global politics and business to science and technology—Subscribe to Economist Podcasts+

For more information about how to access Economist Podcasts+, please visit our FAQs page or watch our video explaining how to link your account.