On September 30, HM Treasury announced that the Chancellor of the Exchequer had appointed ex-Tory MP Mark Reckless to the office of ‘Steward and Bailiff of the Three Hundreds of Chiltern.’ A few days earlier, Reckless announced that he was defecting to the UK Independence Party, and he wanted to seek a fresh mandate from the electorate. Since MPs can’t resign their seats, the only way to trigger a by-election was to resort to a curious legal fiction.
The prohibition against MPs resigning their seats dates back to the seventeenth century. In 1624, the House of Commons resolved that “no man, being lawfully chosen, can refuse the place.” In those days, membership in the Commons was more of a burden than an honor, and so it made sense to prevent people from relinquishing their seats easily.
Several decades later, the Commons resolved “that no Member of this House shall accept of any Office, or Place of Profit, from the Crown, without the Leave of this House, or any Promise of any such Office, or Place of Profit, during such time as he shall continue a Member of this House.” This resolution was motivated by the belief that an MP who was on the Crown’s payroll would be unable to effectively hold the executive to account.
In the eighteenth century, enterprising minds realized that the ban on Crown officeholders could be used to allow MPs to resign. It became customary to use Crown stewardships for this purpose since they were purely nominal offices. Although there used to be a number of these offices, only two of them are still used today: the Crown Steward and Bailiff of the three Chiltern Hundreds of Stoke, Desborough and Burnham and the Crown Steward and Bailiff of the Manor of Northstead. Oddly enough, this arcane practice was preserved by section 4 of the House of Commons Disqualification Act 1975.
In theory, the Chancellor of the Exchequer can refuse an application for appointment to one of the Crown Stewardships, but that hasn’t happened since 1842.
Mark Reckless will hold his new office until it is needed for someone else (in theory, he could ask to relinquish it, but as far as I know, no one has ever tried to do that). But Reckless shouldn’t change his letterhead just yet. If UKIP continues to win these by-elections, it’s possible that there could be a few more appointments to the Stewardship in the coming months.
 The resolution seems to have been a judicial rather than a legislative act, which might explain why it doesn’t appear in the Commons Journal. It is, however, recorded in Sir John Glanville’s treatise on electoral cases. See Glanville, Reports of Certain Cases Determined and Adjudged by the Commons in Parliament (London: S. Baker and G. Leigh, 1775), 101
 Commons Journal, vol. 9, 30 December 1680.
 This prohibition was bent for MPs who were Ministers of the Crown. Until the early twentieth century, an MP who became a Minister had to seek re-election in a special by-election upon taking office (the prohibition only applied to sitting MPs—there was nothing to stop someone who already held a Crown office from being elected to the Commons). The Re-Election of Ministers Act 1919 curtailed the practice, and it was finally abolished for good in 1926.
 In 2011, Gerry Adams tried to resign his seat by writing a letter to the Speaker, but he was nevertheless appointed to the Manor of Northstead in the usual manner. Adams, a member of Sinn Fein and a dedicated republican, reacted by refusing to recognize his appointment.