For two hundred years, the abolition of slavery in Britain has been a cause for self-congratulation - but no longer. In 1807, Parliament outlawed the slave trade in the British Empire, but for the next quarter of a century, despite heroic and bloody rebellions, more than 700,000 people in the British colonies remained in slavery. And when a renewed abolitionist campaign was mounted, making slave ownership the defining political and moral issue of the day, emancipation was fiercely resisted by the powerful 'West India Interest'. Supported by nearly every leading figure of the British establishment - including Canning, Peel and Gladstone, The Times and Spectator - the Interest ensured that slavery survived until 1833 and that when abolition came at last, compensation was given not to the enslaved but to the slaveholders. Worth e340 billion in today's money, this was the largest pay-out in British history before the banking rescue package of 2008, incurring a national debt that was only repaid in 2015 and entrenching the power of slaveholders and their families to shape modern Britain. Drawing on major new research, this long-overdue and ground-breaking history shows that the triumph of abolition was also one of the darkest episodes in British history, revealing the lengths to which British leaders went to defend the indefensible in the name of profit.