Even the very earliest anti-slavery campaigners understood how important a display of objects could be. The pamphleteering Quaker, Thomas Clarkson, one of the first and foremost British protesters against the trade, filled a chest with African artefacts, tropical products, manacles and whips and toured the country delivering impassioned public speeches. Britain ought to be trading with Africa for goods and not for people, he argued. His visual aids had a galvanising effect and hundreds of petitions started pouring into the House of Commons.

This week, as part of the bicentennial commemorations of the passing of the 1807 Act that led to an end to a trade in enslaved Africans using British ships, the International Slavery Museum opens in Liverpool. A concise display, formerly in the basement of the Maritime Museum, has been expanded to take over three prominent gallery spaces.

It joins the Wilberforce House Museum in Hull as a significant museum devoted to the history of slavery. In November Museum in Docklands will open London, Sugar and Slavery, the only permanent gallery in London that examines the city’s involvement in transatlantic slavery. Breaking The Chains, a major slavery exhibition, currently occupies a floor of Bristol’s British Empire & Commonwealth Museum.

“Never again” is the impassioned message of the Liverpool museum. The millions of people who were transported from sub-Saharan Africa, as well as all those left behind, were subjected to unimagina-bly terrible levels of cruelty, dislocation and cultural devastation.

The museum reiterates all the well-known, but none the less appalling, facts of transatlantic slavery beginning with the raids along West African coasts that saw herds of terrified tribespeople driven towards ports. There they would be loaded onto ships that transported them in atrocious conditions across alien oceans to the plantations where they would labour in shackled servitude for the rest of their lives. It studies the economics of this inhuman trade, the part that the slave port of Liverpool in particular had to play in it, and the role of the merchants who grew rich on the strength of what came to be known as “the abominable traffick”.

The objects on display have become the repositories of some of Western culture’s most shaming memories. Here are the forked wooden yokes that controlled stumbling captives, the cowrie-shell trinkets that betokened all their lives were worth, the plans of the ships that carried them in the cruellest and most insanitary conditions, the tables of figures that reduced them to so many financial tallies, the irons that bit into bound wrists and ankles, and the muzzles and head-braces that were applied as punishment.

The West may have denied these enslaved Africans their voice, but these artefacts speak with a horrifying force. Wince at the dainty woman’s whip with its neatly plaited thongs and its fancy silver handle. This instrument of cruelty would have been sported like some delicate fashion accessory by a plantation owner’s petulant wife. Compare the back-breaking hardships, the brutal monotony, the cultural pillage and routine rape of the plantation slave’s life with the comforts that the white beneficiaries enjoyed as they took up their silver sugar nips to pop refined cane lumps into porcelain tea cups or flavoured their rich food with the tempting spices. Their luxuries were the byproducts of a lucrative trade in human life.

And yet, too many of the artefacts that now go on display lack the museological equivalent of Clarkson’s commentaries. Although there are plenty of contemporary testimonies and rousing quotations, touch-screen video monitors, explanatory models and display panels, too often they are far too brief. This museum seems more geared to the school children who will be tempted to rush from one eye-catching exhibit to the next – from the mud-hut recreation to the showcase of manacles, from the Ku Klux Klan costume to the karaoke-style music deck – than to the adult who wants to understand in depth the terrible trade that laid the foundations of so much of our modern world. The history of transatlantic slavery is one of subtle complexity as well as enormous import.

It is not that the museum ignores these complexities, it presents the artefacts of a proud native culture, for instance, but it doesn’t really succeed in redefining this awkward colonial ethnographic collection. Jumbled cases of tribal carvings, masks and musical instruments are given only the briefest labels. They may capture a sense of how alien these boggle-eyed totems must have seemed to Western pillagers, how they may have led to the traders assuming that “negroes” were merely subhuman inferiors, but there is precious little to explain the other side of the argument: to give a sense of the true intricacy of the African continent’s native culture.

The West African empire of Mali, for example, was reputed to be one of the largest, richest and most powerful states in the world by the 14th century. You may be struck by the painted wooden carving of a woman cradling her baby, as tenderly evocative as any Christian Madonna and child. But its deeper resonances so easily get lost in the muddle. It should be accompanied by some explanation of the exalted role of motherhood in African culture which, in its turn, could lead on to a more profound sensibility of the particular degradation that enslaved women suffered.

The show does not shrink from touching upon several uncomfortable, awkward and controversial issues. It looks at the role that Africans themselves played in the trafficking of their fellow people. But the visitor has to search hard to probe the underlying complexity. A gun is not accompanied, for example, by an explanation of the way that traders encouraged lucrative tribal conflicts through the sales of arms and ammunition. “I verily believe that the far greater part of the wars in Africa would cease if the Europeans would cease to tempt them with goods for slaves,” wrote one slave-ship captain. And look at the golden regalia of the Asante. What was the effect of the slave trade on the thinking of Africans? Did it help to spawn these corrosive dreams of great wealth?

This museum is most moving where it ventures beyond the mechanics of a barbaric business venture to look at the emotional implications. One of its most powerful messages is that these people were not simply victims. Indomitable captives fought with courage and spirit to keep their identity in the face of terrible odds. The history of slavery could be written as a story of resistance, as a tale of shipboard revolts, of “maroon” communities (isolated groups of escaped slaves), secret sabotage and stubborn native memories that fought to preserve a suppressed cultural inheritance.

From the rebellious despair of the suicide to the successful 1791 revolution, which led to the establishment of the independent black republic of Haiti, this is a tale not just of subjection but also of unbroken spirits.

This, in the end, is perhaps the most powerful legacy of this show. And the legacy matters. History comes to contemporary life in a final section that looks at anything from African role models to carnival traditions and gangster rap songs.

But, before we can see how much history has truly taught us, we must wait until 2010 for the second phase of this project to open, with its accompanying research and education centre. The transatlantic slave trade may have been abolished, but slavery still thrives in our modern world, and the new centre promises to address this. It seems that we must remain on our guard, or we will not truly be able to say “never again”.

— International Slavery Museum, Albert Dock, Liverpool L3 4AQ. 0151-478 4499; www.liverpoolmuseums.org.uk/ism

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