We don't even have to stay at this level, we could drill down further. How England's system of law differed from Rome's, how their economic system differed and what effects that all had on their politics and the ambitions of would-be tyrants. You both seem to just want to look at the politics. England's common law provided a grassroots bulwark against tyranny, tyrants like to implement legal codes but that ability was limited, constraining important powers like tax collection. Their innovations concerning contracts and charters and financial instruments forced their kings along certain lines. They simply had a more well-developed civic infrastructure that allowed it to heal when damaged whereas Rome's crumbled.

All of these things are connected, they all contribute to rule of law.