This book brings together a selection of law suits brought by peers and members of the house of commons in the royal common law and equity courts at Westminster between 1377 and 1512. Many of the documents edited relate to aspects of constitutional history, such as disputes over parliamentary elections, the payment of the wages of members of the commons, and the evolution of the parliamentary privilege of freedom from arrest, while others illustrate a variety of aspects of the life of the medieval parliament and the members of both houses. The texts gathered within have not hitherto been published, and have been collected from unwieldy and often poorly accessible sources among the English public records. Full modern English translations of Latin, French and Middle English texts have been printed as parallel texts alongside transcripts of the originals, thus making the material accessible to a readership beyond the specialist in medieval legal history.