It is the monarch herself (or himself) who enacts each new law. As was said a long time ago, when Parliament creates a new statute, "the King is pars agens, the rest [i.e. the Lords and the Commons] are but consentientes" (Ship Money Case (R v Hampden) (1637) 3 State Tr 826, per St John in argument). Halsbury's Laws states:
The United Kingdom Parliament is sometimes described as bicameral. This is true in the sense that it has two chambers, the House of Lords and the House of Commons, but in law it also has a third part, the monarch, with whom lies the power of enactment, by and with the advice and consent of the three estates of the realm in Parliament assembled....In 1820, Chitty wrote in A Treatise on the Law of the Prerogatives of the Crown:
Though the King is said to be the caput, principium, et finis of Parliament, he is but a part of it, and, per se, possesses no legislative power.... In a constitutional point of view, however, the legislative power is lodged in the King, subject to the assent of the Houses of Parliament. Laws are said to be enacted "by the King's Most Excellent Majesty, by and with the advice and consent of the Lords Spiritual and Temporal and Commons in Parliament assembled."The enactment formula cited by Chitty is almost the same as the one used today. This is the present-day formula:
Be it enacted by the Queen’s most Excellent Majesty, by and with the advice and consent of the Lords Spiritual and Temporal, and Commons, in this present Parliament assembled, and by the authority of the same, as follows....The earliest words of enactment, used in the mediaeval period, were "Purveu est" or "Provisum est" ("It is provided" in law French and Latin). The roots of the present formula date back to the 14th century. It had nearly completed its evolution by the start of Charles II's reign in 1660, and the enactment formula in the Habeas Corpus Act 1679 is nearly the same as the present-day one:
For the prevention whereof, and the more speedy relief of all persons imprisoned for any such criminal or supposed criminal matters; be it enacted by the King's most excellent majesty, by and with the advice and consent of the lords spiritual and temporal, and commons, in this present parliament assembled, and by the authority thereof....