History in making as Trump, Kim Jong-un meet

North Korean leader Kim Jong-un and US President have been in Singapore for a day, and are about to meet. North Korea has said it is willing to commit to denuclearisation - but that term is open to interpretation. It's also unclear what concessions Pyongyang could demand in return, which analysts say makes the summit very hard to predict. Our Washington correspondent Harry Horton looks ahead to the historic summit.