Who amongst us has not felt goosebumps listening to Martin Luther King’s electrifying “I have a dream” speech? That speech was delivered to a quarter-of-a-million people at the end of the March to Washington on August 28 1963. Its central passage was inspired, it is said, by the gospel singer Mahalia Jackson shouting at King to “tell them about the dream”. A masterpiece of public oratory, it evokes a millennial vision of equality, justice and peace, of honour, validation and redemption. He drew on the Bible and the US Constitution, his gospel music call and response incantation building intensity and fervour to a heart-bursting, spine-tingling climax. Preacher, prophet, visionary, leader, we know him so well because that speech sang.

Of course, sometimes time and tide just coincide. Great movements of population in the US after emancipation brought African Americans to the great industrial cities, places where the old order’s hold was less secure and where education, slowly but surely, sparked an awareness of rights and a growing stubbornness in the face of prejudice and injustice. Men who returned from fighting in World War II and Korea found it hard to go back to being called boys. Women like Rosa Parks decided not to give up the seat on the bus. Protest movements and songs reignited the militancy of the dustbowl refugees, but for a new generation and a new crusade.

The outlines of Martin Luther King’s history are well rehearsed. He was, by all accounts, a precociously intelligent youth, entering higher education at 15 years of age. Although at first a reluctant recruit to religious ministry, having concluded that the church offered the most assuring way to answer “an inner urge to serve humanity”, he became a minister in the Baptist Church. But it is for his central role in the civil rights movement that he is remembered and, of course, for the manner of his death 50 years ago, shot in Memphis by white supremacist James Earl Ray.