Having been hatched, the law grew fast and fit, and soon took flight. Originally the king's council had carried out executive as well as legislative and judicial functions. Over time, royal courts split off from the council and were established as separate entities at Westminster Hall. Built by William Rufus, and later enlarged and re-roofed by Richard II, its enormous dimensions – three hundred feet long with a high, beamed roof – could accommodate a plethora of royal courts. By the mid 1160s ordinary litigation was being transacted before the king's justices at Westminster. But there could be lengthy absences. It was not until 1339, after a six-year interlude in York, that the location of the royal courts in Westminster Hall became permanent.

The first department of state established there was the Exchequer, which took its name from the chequered table at which it sat. Moving from Winchester to Westminster at the end of the twelfth century, it took up residence in a separate chamber adjoining the Hall. In its judicial role the Exchequer originally dealt with disputes over Crown revenues, but gradually extended its jurisdiction to disputes between individuals on many subjects. Its meticulous work required written records. From 1130 it got them in the form of pipe rolls. The other royal courts would follow suit, producing the plea rolls.

Near the entrance of the Hall was the Bench or Common Bench, later called the Court of the Common Pleas. It was the main royal court for ordinary civil litigation and by far the busiest. It developed out of the Court of Exchequer, separating from it in the 1190s.