This month, June 2015, is the 800th anniversary of the signing of Magna Carta. Everybody has sort of heard of this "great charter," which has something to do with English liberties or something. Well, sort of.
It starts with King John of England (not John I, just John, because he has been so reviled that no one wanted to be named for him). His barons were enormously irritated with him. His worst failing was that he had lost Normandy in a disastrous war with France. The English nobility had, for the most part, also been lords of Norman lands, ever since the Norman Conquest of 1066, and now those lands were gone.
John was never supposed to be king. He was the fifth son of Henry II and Eleanor of Aquitaine. Their oldest son (William) had died as a child, but four more grew to adulthood, Henry, Richard, Geoffrey, and John. But the next three died (mostly in battle) without surviving sons--Geoffrey had actually had a son, Arthur, but young Arthur had mysteriously disappeared, being last seen with his Uncle John, while Richard was king and Geoffrey was dead. John didn't even get to have a good ancestral name, like his brothers, being named John only because he was born on Saint John's day (June 24).
John had also irritated both the barons and the bishops of England by making high-handed decisions without consultation, by seizing property of some people who bothered him, by imprisoning other people who bothered him, by initially not letting the new archbishop of Canterbury back into England after he visited Rome, by raising taxes, and by playing favorites with people the barons hated. Enough was enough. At a place called Runnymede, in June 1215, the archbishop and the barons forced John to sign a charter, the Magna Carta, listing all the things he wouldn't do anymore.
Understandably, John hated this. He got the pope to declare it null and void by promising that he would treat England as a fief held from the pope and would go on Crusade very soon. But John died the next year, and the barons had baby Henry III (John's son) sign it again. Ever since then, Magna Carta has been taken as a symbol of English liberties. Modern England doesn't have an actual constitution, as does the US and most other countries, but rather a series of documents that are considered to be "like" a constitution between them, and Magna Carta is the first one in the collection. In a way this is rather ironic, because almost everything it says has been formally repealed.
So what is in it? First of all, it has nothing to do with jury trials. Secondly, it has even less to do with Parliament--Parliament, a more formal version of the councils all medieval kings were expected to call regularly, came along three generations later (see more here on Parliament). Sorry to disappoint you.
A lot of Magna Carta (the part that no one pays attention to anymore) named specific people who the barons wanted to get out of the royal court, talked about navigable rivers, and regulated royal authority over heiresses too young to inherit. Nothing in it discussed the "common man." It did stress that the king could not imprison people on a whim (could not "deprive them of liberty" without "due process of law"), could not make important decisions without proper consultation, and especially was to leave both the Church and the city of London free to carry out their own business and make and follow their own laws. This declaration of freedom for Church and London is still in force today.