While rule of law, limited government and customary rights for the comman man are a big part of the English (and Anglosphere-wide) self-image, looking at medieval Europe tends to obscure some of this alleged English distinctiveness.
Classical traditions of English historiography cite the English as becoming distinctively more committed than other Europeans to rule of law, limited government and personal liberty by the time of the Magna Carta in 1215. Other traditions trace these characteristics back further to allegedly more egalitarian pre-Norman Anglo-Saxon England.
However, the more one looks at the histories of other European countries, the less uniquely English all these traits begin to appear.
Most medieval European states had a mix of monarchy and assemblies. Poland, Hungary and the Holy Roman Empire all had constitutionally limiting documents and traditions. Where England had its parliament, the HRE and Hungary had their Diet, Spain had the Cortes and Russian principalities had their Dumas. Kingship was often elective throughout Europe.
It seems that systems of mixed constitutions were ubiquitous in most European states rising from the collapse of the Roman Empire. One could call this a common Germanic tradition – later adopted by Slavic states. But if you go back further there’s the longstanding tradition of the Senate, from Rome’s early days through Byzantine times. So, this makes assemblies of nobles and leading citizens as a check on monarchical power at least an Indo-European tradition (at least for the European branch and possibly excluding much of the Indo-Iranian cultural sphere.) Depending on the organization of tribes at various points of development a mixed constitution may be as much the human norm as absolute despotism, if not more so.
Plus, in English history, strong monarchs would often marginalize parliamentary authority or impose their own judicial rules like Star Chambers.
So, that's why I posed the question. (in part its why I posed the questions in my unfortunately worded Russian and Spanish poll threads also) when in its history can we see England clearly diverge from France, Spain, the HRE and Russia as clearly a country of greater liberty? And what specifically about English governance at that time supports dating English distinctiveness to that point in time.