In October the Guardian published a striking collection of photographs chronicling the history of black Britain from the 1890s until today. It was introduced by Stuart Hall, an academic and broadcaster who came tenth in the 2003 poll to find the top "100 Great Black Britons".

He wrote that all too often it is assumed that black settlement in Britain "began only the day before yesterday", when in fact it has spanned over 400 years. The legacy of slavery and colonisation means that this has been a "long, difficult, sometimes bitterly contested and unfinished story".

One character in this story is Olaudah Equiano (1745-97). His face is on the stamp issued in 2007 to mark the bicentenary of Britain's abolition of the Atlantic slave trade. Equiano's efforts to bring this trade to an end led to him being voted fourth in the roll call of black Britons.

It also explains why he is currently centre stage at Birmingham Museum & Art Gallery in Equiano: An Exhibition of an Extraordinary Life. It is based on his more modestly titled autobiography, The Interesting Narrative of the Life of Olaudah Equiano or Gustavus Vassa the African. It was published in 1789 and became a bestseller.

Equiano's alternative name - Gustavus Vassa the African - was given to him by his slave masters. It is fitting that this exceptional man should have been called after a king, Gustav Vasa of Sweden.

For Equiano was born the son of a tribal chief in present-day Nigeria. He was kidnapped at the age of about 11 and taken across the Atlantic to Barbados. Equiano proceeded to travel the world - first as a slave, then as a free man. He eventually settled in London and it is here that the exhibition begins.

The curators tell Equiano's story in reverse, with the main character looking back on his eventful life. So, from London, we are taken back to west Africa before the arrival of the slave traders.

Equiano described his rural upbringing as both cultured and peaceful. This was an important retort to those who justified slavery on the grounds that Africa was savage and uncivilised. The exact same people later sought to discredit Equiano's account by claiming that he was actually born in the West Indies.

The exhibition at Birmingham explores this, presenting the evidence for and against. Another unresolved issue includes the identity of the famous 18th-century portrait in the collection of the Royal Albert Memorial Museum in Exeter.

This was once considered to be Equiano, but new research suggests that it depicts another stylishly dressed black man, perhaps the writer Ignatius Sancho (1729-80).

The exhibition is divided into seven themes, and the layout is somewhat complicated. The neat little booklet given to all visitors provides a much-needed guide.

The gallery features a series of numbered "light-towers", which introduce the various sections. These feature extracts from Equiano's autobiography together with brightly coloured linocuts by Chris Wormell.

Aside from copies of his book, very few artefacts connected directly to Equiano still exist. So the curators have had to take a lateral approach to the choice of objects on display.

One example is the recreated "freedom suit" that Equiano bought to mark his liberation in 1766, but was lost some time ago. Elsewhere, items of a similar period and type serve as stand-ins.

The most touching is a broken tumbler cup on loan from the St Eustatius Historical Foundation. This represents the first commodity independently traded by Equiano for a tiny profit.

In the context of this exhibition this fragile, inanimate little thing becomes a moving symbol of Equiano's long and immensely difficult path to freedom.

The human scale of slavery

There are many unfinished stories and hidden histories in this excellent exhibition. It succeeds because it focuses on one person, someone who, by his own account, was "neither a saint, a hero, nor a tyrant".

This gives us a personality to relate to, reducing the terrible enormity of the slave trade to a human level. But it does this without simplifying history. It shows, for example, how a gun made in Birmingham could become a part of the slave trade.

We often associate slavery with the great ports of Bristol and London. But Birmingham's produce was also linked to slavery.

This was why the Atlantic slave trade was such a complex issue: far from the plantations and the slave ships, businessmen in Birmingham were working to keep their companies going - and supporting slavery in the process.

Cogs in a machine

Towards the end of his life he undoubtedly played a pivotal role in the abolition movement. Yet in his autobiography Equiano reveals that in 1776 - 10 years after he had secured his own freedom - he travelled to what is now Nicaragua and helped establish a plantation worked by slaves.

Some curators would no doubt have preferred to skip over this in an attempt to celebrate Equiano's considerable achievements. But that would have been a mistake.

It is too tempting to see history in dualistic terms. Yes, Equiano was a great man, but he had failings too - and that makes him all the more human, reminding us that even tiny cogs can make an enormous difference.

The most amazing thing about Equiano is that his name is known at all today. That he did not vanish from the record books, like so many slaves, means that he stands as a representative for all those that have been lost to memory.

Birmingham has done well to begin telling one version of this vital story. It has done so not only through this exhibition, but also a whole host of other related activities, including a catalogue, website, outreach programme and basic travelling exhibition.

Even so, it is disappointing that because of cost and the fact that many of the objects are on loan, the full version of this thought-provoking exhibition will not be touring - as Equiano himself did with an epic book tour to promote his Interesting Narrative.

Stuart Burch is a lecturer in museum studies at Nottingham Trent University

Project data

Cost: £878,000

Main funders: Heritage Lottery Fund £653,000, Birmingham City Council, Museums, Libraries and Archives Council

Partners: Birmingham Museums and Art Gallery, Equiano Society

Curator and project manager: Clare Parsons

Exhibition design: Houghton Kneale Design

Exhibition ends: 13 January 2008