Edward Chambers was one of the largest slave-owners in the parish of Hanover, with almost 800 slaves in three plantations encircling the port of Lucea, from where Africans were unloaded to toil in the cane fields of North-West Jamaica. In mid-July 1776 he suddenly realised something was up. He learnt that the overseer's boy was ordered to fill his master's pistols with black sand instead of powder. Then Chambers’ personal servant suspiciously entered his room one morning, first on the pretence of wanting to clean his shoes, then to brush his coat. Disturbed by his bustle and slightly odd behaviour, Chambers peeped from under his mosquito net to discover a pistol levelled at him. He grappled the gun away from his valet, who fell to his knees ‘in a tremor’, so the report ran, and confessed to a plot that implicated many of the estates along the coast; by all accounts, over forty estates whose slaves numbered over 8,600. The valet's task was to dispatch Chambers with a gun or an axe, preferably when he was sitting on the toilet. Bells or guns at Batchelor's Hall would alert others that Chambers had been assassinated. Smoke signals from the burning cane-fields would ignite the insurrection along the coastal plantations. Once three or so estates were taken, so the rebels hoped – and they targeted two of Chambers’ estates and Richard Haughton's Baulk plantation a few miles inland from Lucea Bay – the momentum for a general rebellion would swell. The immediate object was for headmen to seize local supplies of guns and powder, ‘put to death all the white people they could’, and raise the tocsin of revolt in the contiguous parishes of Westmorland and St James.

The Hanover conspiracy had been hatched a month earlier, by drovers, carters and elite workers who had opportunities to communicate among the different estates up and down the coast. Over 55 per cent of these estates housed 150 slaves or more, the average number per proprietor being 220. The plan was communicated and co-ordinated at local forges and stills, and at gatherings that planters believed to be innocuous, such as the funeral of a ‘negro wench’ called Sarah who lived out her life at the Tryall estate with 200 other slaves.