The Bill of Middlesex was a legal fiction used by the Court of King's Bench to gain jurisdiction over cases traditionally in the remit of the Court of Common Pleas. Hinging on the King's Bench's remaining criminal jurisdiction over the county of Middlesex, the Bill allowed it to take cases traditionally in the remit of other common law courts by claiming that the defendant had committed trespass in Middlesex. Once the defendant was in custody, the trespass complaint would be quietly dropped and other complaints (such as debt or detinue) would be substituted.