Our democracy started with the Magna Carta, methinks, but that was control of the sovereign by the Barons. Being judged by one's peers was literally that, the Peers, not the later meaning of peer as a person of the same class.
The current representative Parliament, I guess, came about at the end of Cromwell's dictatorship, but I don't know any details of that at all. It isn't a pure democracy as per the ancient greek definition. {where supposedly ALL the citizens voted on everything (?) } {note the slaves didn't get a vote}. {did the greek women have a vote ? }