Tim Worstall's Sunday Evening Thought:
In English law 'time immemorial' is defined as 1189. So we've actually had people making and passing laws since then, adding all the time.I'm cross posting the comment I made there:
817 years and counting. When do you think they will get the job finished so that the politicians will all go home?
Henry II came to the throne in 1154, when there was still Trial by Ordeal. When he died, in 1189*, there were circuit judges, juries, the King's Bench, the law of tort and so on. Henry II repays investigation, and W.L. Warren's eponymous book is a good place to start.
P.J. O'Rourke asked the "Are they through yet" question in his book Parliament of Whores, at least a decade ago (I can't be bothered to look up the publication date).
The answer still seems to be "no".
Interesting to reflect, in passing, that the rights of jury trial and habeas corpus that were initiated and codified by a mediaeval monarch are being eroded by a bunch of elected tyrants. The Republican case is now made most strongly not by any discontent with the way the monarch carries out her role, or by opposition to the hereditary principle, but rather by the reflection that these bastards are not fit to wield the Royal Prerogative. Parliament should only have limited powers, not essentially those of an absolute monarch.
*I actually wrote 1190, but think the above date is correct. If I remember, he died at Christmas and Richard I wasn't crowned until 1190, which is why I put this as the date of HII's death.