In sketching a picture of the slave trade, the British never asked former slaves what it was like

The Privy Council’s report on the slave trade . . . was a vast document, 890 large pages long, compiling interviews, tables, letters, reports, accounts, colonial and British laws, surgical journals, muster rolls, land surveys and ship dimensions. It contained the results of fourteen months of interviews with fifty witnesses, detailing–amid a forest of economical and geographical data–the killing of unsaleable slaves, the torture of rebel slaves, the dejection and disease of all slaves, the treatment of ‘mistresses’, the conning of sailors into the trade and marooning them in the Caribbean when slaves were unloaded. What it did not include, however, except for a short letter from [Olaudah] Equiano, was any testimony from a black person. Parliament solicited the opinions and stories of soldiers and doctors, merchants and ministers, colonial governors and even the curator of a museum in Stockholm, but at no point in the course of the investigation was it thought necessary to obtain the information and experiences of slaves themselves, although there were hundreds of former slaves at hand in London. It is not clear whether this is because the prejudice of MPs was so entrenched that abolitionists knew they would not listen to black voices, or whether the prejudice of abolitionists themselves was so entrenched that it simply never occurred to them that the slaves might have something useful to add to their researches into slavery. Either way, the most well-informed witnesses with the greatest right to testify were never heard, depriving us forever of a record of their experiences. (73)

Stephen Tomkins, in William Wilberforce: A Biography, on the report presented to the House of Commons on 25 April 1789 to propose the abolition of the slave trade in Britain.