Overview
The Derby Dilly was a name given to a group of dissident Whigs who split from the main party under the leadership of Edward, Lord Stanley on the issue of the reorganisation of the Church of Ireland in 1834. Stanley and three others resigned from the cabinet of Lord Grey on this particular issue but other factors included their fear that the Whigs were appeasing their radical and Irish allies with further reforms.
The group's name 'Derby Dilly' is a reference to Stanley being the heir of the Earl of Derby.
Formation
In 1830 Lord Grey had formed a government that had achieved political success by passing the Reform Act 1832 and abolishing slavery in the British Empire. However, it was an unstable coalition composed of Whigs, Canningites, Radicals, Irish Repealers and Tory mavericks. It had achieved a crushing electoral victory in 1832 against a demoralised Tory party but then quickly fell factional fighting. Lord John Russell wanted to extend the cause of reform to other areas of governance but others like Lord Stanley feared the growth of radicalism and in particular the influence of the Irish Repealers led by Daniel O'Connell. In May 1834, the pressure became too great and Stanley, with Earl of Ripon, Sir James Graham and The Duke of Richmond resigned from the cabinet on the issue of proposed changes to the structure and finances of the Church of Ireland.
Preferring to call themselves 'Moderate Whigs' or just 'Moderates', Stanley and his immediate cohorts including Graham and Francis Burdett, at first, remained on the government benches in the House of Commons. They were at first known unofficially as the 'Stanleyites', as they seemed more of an old-style parliamentary faction that was familiar in British politics from the 18th and early 19th centuries. However, the group soon received a new name from its political opponents to which they are now best remembered: 'The Derby Dilly'.
From Wikipedia (CC BY-SA 4.0).