In April 1988, on the first Chilean live television programme to feature opposition candidates during Augusto Pinochet's regime, Ricardo Lagos became the nemesis of a dictator.

He said: "Realistically, the night of the 'no' vote is the beginning of the end of the dictatorship... General Pinochet has not been honest with his country. First you said, General Pinochet, you had a timeline and imposed the constitution of 1980, I will remind you, General Pinochet, that you said on the day of the 1980 plebiscite: 'President Pinochet would not be a candidate in 1989'. And now you would have the country pass through another eight years with torture, assassinations, with the violations of human rights .... To me, it is inadmissible that a Chilean would have such ambitions to power, to be so bold as to stay for 25 years in power."

Sir David Frost talks to the former president of Chile, Ricardo Lagos, about his groundbreaking interview on Chilean TV, where he publicly denounced General Augusto Pinochet. Why did Lagos speak out on that day? What was the impact of his action? And can a television interview change the world?