Psychologists break down the mysteries of Donald Trump's handshake

Donald Trump’s handshakes have become something of an international curiosity – and now, psychologists have broken down the "tactical" move. The president's unique grip raised eyebrows during his visit to a Nato summit last week, where he appeared to painfully twist the arm of French President Emmanuel Macron. Ahead of the opening of the new Nato headquarters in Brussels, Mr Trump grabbed the French president’s arm hard enough to jerk him to the side.