It is an enormous pleasure to welcome the publication of this, the twelfth set of volumes in the History of Parliament series covering the House of Commons, and the fourteenth set overall. The period covered in these nine volumes forms one of the most complex, violent and disrupted in English and British political history. It has long been a challenge to historians to disentangle those complexities and properly to understand the events and their meaning. It is no accident that it has attracted some of the greatest minds and produced some of the greatest works of British historiography.

Our work, as ever, owes a huge amount to these previous scholars, and their scholarship. That includes the pioneering work of D. Brunton and D.H. Pennington, whose Members of the Long Parliament was published in 1954 and is one of the earliest attempts at a comprehensive prosopography of the English parliament, following the work of Josiah Wedgwood in the 1930s covering the later fifteenth-century parliaments, and coming just three years after the re-establishment of his History of Parliament project on a new and more secure footing in 1951. Our work also owes a good deal to that of the Yale Center for Parliamentary History, whose editions of the diaries of the early years of the Long Parliament have been essential materials for the compilation of these volumes. We owe much, too, to the writings of scholars such as David Underdown, Blair Worden and Austin Woolrych, who mapped out new approaches to the parliamentary politics of the 1640s and 1650s during the 1970s and early 1980s; and to many others who have contributed on specific issues or figures or movements: our reliance on those works will be very evident from the text.

Yet while they build on that hugely important body of work, these volumes now add immeasurably to the available knowledge about the politics of the English civil war and interregnum and represent what may be the greatest quantity of new fully researched data made available since the nineteenth century. We believe they have the capacity to transform the study of the period.