Definition
Parliamentum Diabolicum (Latin: "the Devil's Parliament") is a historical designation for a specific English parliament convened at Coventry in 1459, during the reign of Henry VI (38 Hen. VI). The parliament is remembered primarily for its sweeping acts of attainder passed against the Yorkist lords — including Richard, Duke of York, and his principal allies — stripping them of their titles, lands, and rights. The session was convened by the Lancastrian faction at a time when Yorkist strength made a session at Westminster politically or militarily impracticable, and its proceedings were widely regarded, particularly by Yorkist contemporaries and later chroniclers, as a corrupt or partisan manipulation of parliamentary process rather than legitimate legislation.
The name is a term of opprobrium, not an official designation. It reflects the condemnation of the parliament's proceedings by those who suffered under its attainders and by later writers sympathetic to the Yorkist cause.
Why It Matters in Research
This term is almost exclusively encountered in historical legal research involving the constitutional and parliamentary history of fifteenth-century England, the Wars of the Roses, or the law of attainder. Researchers consulting primary or early secondary sources should be aware of several navigational issues.
First, the term appears inconsistently across historical sources. Some sources refer to the parliament simply by its regnal year and location (38 Hen. VI, Coventry), while others use the pejorative Latin designation. Cross-referencing both forms is essential when searching manuscript records, rolls of parliament, or early printed digests.
Second, the attainders passed at this parliament were subsequently reversed by Yorkist parliaments after Edward IV took the throne in 1461. This reversal-and-counter-reversal pattern is significant for any research into the land titles, peerages, or legal status of families affected by the proceedings, as the legal effect of the attainders was contested and intermittently operative across a roughly two-decade span.
Third, the term sits at the intersection of parliamentary history, constitutional law, and the law of attainder. Researchers approaching it through a purely constitutional lens may miss its significance in the context of peerage law and real property transmission; those approaching it through the law of attainder may overlook its broader significance as an example of parliament's use as a political instrument during a period of contested sovereignty.
Finally, the Parliamentum Diabolicum is sometimes cited in general historical literature without precise legal analysis, which can create confusion about what the attainders actually accomplished as a matter of law versus what contemporaries alleged about their procedural validity.
Historical Dictionary Support
Rapalje & Lawrence identify the term tersely: "A parliament held at Coventry, 38 Hen. VI." The entry does no more than fix the event and its regnal date, offering no analysis of the attainders, the political context, or the reasons for the designation. This is representative of the treatment the term receives in legal dictionaries of the period — recognized as a term of art worth recording, but handled as a historical curiosity rather than a subject for legal analysis.
The brevity of the Rapalje & Lawrence entry reflects the term's status in legal reference literature: it is a proper noun attached to a singular historical event, not a generative legal concept capable of producing doctrine. Legal dictionaries record it largely for completeness, while the substantive historical and legal analysis has lived in parliamentary history scholarship and works on the law of attainder.
What the historical dictionaries miss almost entirely is the downstream legal significance of the session — the subsequent reversals, the effect on real property chains of title, and the constitutional questions raised about the legitimacy of parliamentary attainder as a tool of factional politics.
Jurisdictional Note
This term is specific to English legal and parliamentary history. It has no application in American law or in legal systems outside the English common law tradition. It will appear in research contexts involving English constitutional history, the medieval and early modern law of attainder, or the history of Parliament.