The author, who is professor of history at Pittsburgh University, admits that he found this “a painful book to write”. This does not surprise, for the slave trade has no redeeming features. Reading it has not been a comfortable task either. Unlike, for example, the story of the British Empire, over which one can argue for good as well as bad features (even in this anti-imperialist age), nothing can ever justify the enslaving of one person by another. For 400 hundred years rich Western countries – particularly the English – plundered the west coast of Africa for “black gold”: men, women and children from the indigenous tribes who were kidnapped, shackled and forced-marched to the slave ships that transported them to the plantations of America and the Caribbean. This helped to enrich the oppressors and to pauperise the countries of the oppressed – a legacy which has left deep scars on both sides of the Atlantic.

It has been estimated that in these four centuries over 12 million people were loaded onto slave ships; of these, over one million died in harrowing circumstances. The years between 1700 and 1809 are the author’s particular focus, for two thirds of the total transportations belong to this era. His book coincides with the 200th anniversary of the abolition of the slave trade. In contrast to the drama and romanticism of a film such as Amazing Grace, it is a sober and detailed piece of research into every aspect of these infamous transports: the ships, the captains and the crews, as well as the institutionalised violence done to their captive cargo. Cruelty, the author comments, was intrinsic to the trade. As was observed by an abolitionist, “the captain bullies the men, the men torture the slaves [and] the slaves’ hearts are breaking with despair.”

We learn sinister details such as that sharks always followed the slave ships, attracted by the offal, the dead bodies both of captives and sailors (who had their own mortality rate) and the living who accidentally fell overboard or who were thrown into the sea as a punishment and lesson to the others. There are dire accounts of the personal sadism of captains, who had total power over the lives of crew and slaves, who would select women slaves for sexual abuse and flog both sexes indiscriminately if they rebelled against their subservient status. Slaves who did not die of disease, suffocation or suicide often succumbed to “melancholy” — despair at their hopeless circumstances — and refused to eat. Sometimes their will to die was stronger than the whippings and force-feedings that the slave captains employed to keep them alive. Dead slaves were unprofitable.

Rediker rarely mentions humanity among the slave captains, though he singles out a Captain James Fraser who was noted for running an orderly ship: he would release the slaves from their leg-irons, and tried to provide them with clean quarters and decent food; he would also try to ensure that friends and relations were not forcibly separated in the slave markets and plantations of the New World. Yet as the author observes, Fraser did this as much for the sake of a greater profit margin as for humane reasons and he chose not to enquire how his human cargo arrived on board. That they had not arrived of their own free will must have been obvious to him, for no African willingly entered a slave ship.

Even otherwise good men saw slavery as being part of the nature of things. John Newton, the slave captain who converted and subsequently wrote the hymn from which the film Amazing Grace takes its name, did not instantly repudiate his trade on becoming a Christian; indeed, it took him 30 years and four slaver journeys. “Slaving,” he long believed, “was the appointment Providence had marked out for me.”

His vivid pamphlet, Thoughts upon the African Slave Trade (1788), which helped ignite the abolitionists, is one of Rediker’s primary sources, with its descriptions of the many fights below decks between men bound together in close quarters for hours at a time, the reeking stench from the “necessary tubs”, the plagues of rats and the corpses shackled to living men. Yet another detailed account was written by a young Oxford graduate, John Riland, returning from England to the family plantation in Jamaica on a slave ship in 1801 and already influenced by the abolition movement. Riland notes that his ship carried 170 men and 70 women, incarcerated for 16 hours a day with no room to stand upright and poor ventilation. The ship was, ironically, called “The Liberty”; the captain warned Riland that “the smell would be unpleasant for a few days”.

The book, primarily concerned with the slave trade itself, only lightly touches on the abolition movement and its key players, such as Olaudah Equiano, who had been captured in present-day Nigeria, aged 11, in 1754, and who was the first African ever to describe his experience of slavery. Wilberforce, who led the struggle in Parliament, relied on the research and support of many others, notably Thomas Clarkson, who visited Bristol in 1787 to gather evidence for the London abolition committee formed that year. His long labours to bring the facts of the Middle Passage before an ignorant public are here shown as heroic.

Probably his most brilliant piece of abolitionary propaganda was a broadsheet with scale diagrams of the slave ship “Brooks”. These pictures of hundreds of bodies lying chained together in an elaborate decking system, together with the engraving of a kneeling slave, his hands clasped together with the caption, “Am I not a Man and a Brother?”, did more than anything else to alert and disquiet ordinary people. The harsh facts of Clarkson’s research spoke for itself.

Rediker explains that the idea of writing this book came to him in the late 1990s when he was visiting prisoners on death row in Pennsylvania.; their plight and the cruelty of capital punishment invited comparison with the millions of lost and blighted lives of an earlier barbarism. He ends with a plea for “a social movement for justice” towards the descendants of the slaves. This strikes me as somewhat vague and impractical – though the civil rights movement in the US still has work to do. Further, though the anniversary of abolition has brought some public apologies for the crimes of our forefathers, such statements seem hot air if not accompanied by practical work to remedy the ills of today, such as the increasing number of East European sex slaves in the UK as a result of illegal immigration. It is also estimated that more than 70,000 Africans have attempted to cross from the African coast into Europe on makeshift rafts in the last four years alone – in desperate contrast to their ancestors’ wish to remain where they were.

Those who fight for the rights of unborn children also draw a parallel with the 20-year battle of the abolition movement 200 hundred years ago for recognition of slaves as fellow humans, and draw comfort from the final victory. It is not an exact parallel, of course, for many well-meaning people see abortion not so much as desirable in itself but as the better option in hard cases. This struggle in the UK – once a foremost slaving nation – has already lasted over 40 years and the end is nowhere in sight. It may be a long time before the unborn are also recognised as “a Man and a Brother” and the deliberate curtailment of their lives seen in the same light as the hapless prisoners of the slave ships.

Francis Phillips writes from Bucks in the UK.