In 1959, a white American writer decided to turn himself into a “Negro”, with the help of a dermatologist. John Howard Griffin would venture alone into some of the Deep South’s most virulently racist hotspots and experience life on the other side of the tracks. Black Like Me is the record of his trip.

That year the American South was still firmly gripped by segregation. All aspects of public life were separated according to race and miscegenation was illegal. African-Americans endured appalling social, educational and economic disadvantages, and although the civil rights movement was growing, any legal victories were still a long way off. Griffin reveals in his opening chapter that he was haunted by the question, “What is it like to experience discrimination based on skin colour, something over which one has no control?”

Before his act of racial reinvention he had already lived an extraordinary life. Although born in 1920 into a genteel Southern family — his father was a wholesale grocer and his mother a music teacher — he was educated at a school in France with some black African students. At the outbreak of the Second World War he was active in the French Resistance, helping Jewish escapers, and later he was stationed in the Solomon Islands for three years with the US Army. Blinded for ten years through shell shock, he wrote two novels on a typewriter before his sight was restored.

The sighted 15-year-old who left Texas carrying the bigoted baggage of his culture returned a blind man who had learnt to relate to people simply as human beings.

His journey into blackness begins with intensive skin-darkening treatment involving oral medication, a sun lamp and dye stain. He shaves his head and is shocked at his image — “A fierce, bald, very dark Negro glared at me from the glass.” Then “with enormous self-consciousness” he stepped from the house into darkness. When he takes his seat at the back of a bus with other black people and nobody bats an eyelid, he realises it has worked — he has passed.

For the next six weeks Griffin travelled through the Deep South and his amazing story exposes the racist treatment meted out to the community to which he now belonged. Stripped of the privileges of being white, he has to walk miles to get a drink of water or use a restroom because local amenities are marked Whites Only. He is forced to stay in inferior lodgings, denied access to most eateries, and offers of work on the phone are rescinded when he turns up in person. He is harassed and insulted by street thugs, and the air seethes with the threat of violence from those who know that discrimination towards “Negroes” is sanctioned and that many crimes, including lynchings, are likely to go unpunished.

Petty humiliations become routine. A bus driver says “Watch your step” to his white passengers but not his black ones. Another makes him wait eight blocks before letting him off. Yet another lets his white passengers use a rest stop on an inter-state journey but won’t let his black passengers because, “I can’t be bothered rounding up all you people when we get ready to go”. One of Griffin’s hardest early lessons was to offer his seat to a white woman standing on a bus. “For an instant our eyes met. I felt sympathy for her, and I thought I detected sympathy in her glance.” Not a bit of it. “Her blue eyes, so pale before, sharpened and she spat out, ‘What you looking at me like that for?’ ... I felt myself flush. Other white passengers craned to look at me. The silent onrush of hostility frightened me.

“She continued to rant: ‘They’re getting sassier every day.’ ”

Then there is his daily encounter with the Hate Stare of white passers-by. “Nothing can describe the withering horror of this. You feel lost, sick at heart before such unmasked hatred.”

Black Like Me brilliantly reveals the dehumanisation of black people by the white majority. But Griffin’s period as a “Negro” was finite, and his white critics argued that he felt “this degradation more deeply than black people” because it was new to him. He replied that prejudice “burns any man ... Such whites say it the way they have seen it but I say it the way I have experienced it.” He also noted that black people did not question the validity of the racism he experienced. In his 1977 book A Time to be Human, he wrote of his 1959 project: “Once a few whites had to speak out for justice and interracial dialogue at a time when whites would not listen to blacks.”

Even in these bleak times, changes were happening. In Alabama, under Martin Luther King’s influence, there was passive resistance, and in Atlanta, Georgia, in spite of segregation there was a powerful black leadership.

When the story broke, initially in a “Negro” magazine called Sepia, there was intense media interest, most of it positive. Out of the 6,000 letters Griffin received, only nine were abusive. The biggest backlash occurred in his segregated home town of Mansfield, Texas. There were death threats and an anonymous caller told his mother: “Why he’s just thrown the door wide open for those niggers, and after we’ve all worked so hard to keep them out.” An effigy of Griffin was burnt in the high street and his family eventually decamped to Mexico.

If his journey had taken place in Britain, how different would his story have been? Postwar immigration from the Empire meant a large expansion in the number of black people living in Britain’s cities. Immigrants experienced discrimination in employment, housing and on the streets. Members of fascist organisations sometimes attacked them, and Keep Britain White graffiti appeared on inner-city walls. But there was no apartheid; blacks and white lived side by side, and with each other.

My parents married in 1955 — a white Englishwoman and a black Nigerian. Opposition to their marriage came from within my mother’s family rather than from the world outside. When they moved into an exclusively white area, their neighbours were welcoming. My mother remembers only once being called “nigger lover”. My father endured far more indignities, but responded in kind: insult for insult, fist for fist. But terrible things did happen: the Notting Hill riots of 1958 were sparked off when Teddy Boys assaulted a white woman they had seen out with her Jamaican boyfriend.

Griffin writes in his epilogue: “They could not see me or any other black man as a human individual because they buried us under the garbage of their stereotyped view of us.” Even though America now has its black President and Britain has black MPs, black judges and black footballers, the people who won the BNP its first two seats in the European Parliament show that even where changes occur, these remain incremental rather than absolute.

Black Like Me is considered a classic on race and is still taught in thousands of American schools and colleges. Robert Bonazzi’s critical study of Griffin’s experiment, Man in the Mirror, fills in Griffin’s back-story and is an excellent contextual companion.

This reissue of Black Like Me marks the 50th anniversary of its publication. As we approach Black History Month it will introduce a whole new British readership to a work that is still an important, illuminating and fascinating read.

Bernardine Evaristo’s novel Blonde Roots is a satire on the slave trade

Black Like Me, by John Howard Griffin, is published on October 5 by Souvenir Press at £12. To pre-order it for £10.80 inc p&p call 0845 2712134 or visit timesonline.co.uk/booksfirst

Times Recommends

• The 100 Best Books of the Decade
• The Times picks the 50 best paperbacks of 2009
• The conversation: James Ellroy