King Richard II exiled Henry of Lancaster, forbade his
inheritance, and took his property. This made all propertied men
anxious. The "Merciless Parliament" of 1388 swept out King
Richard II's friends. Parliament threw Richard II into prison and
elected Lancaster to be King Henry IV. This action established
clearly that royal decrees were subordinate to parliamentary
statutes. The House of Commons became very powerful.

So the roles of Parliament and the King's council are starting to
differentiate into legislative and executive, respectively. The
legislative function is law-making and the executive is
regulation-making that refines and effectuates the laws of
Parliament. But the legislative, executive and judicial
authorities have not as yet become so completely separated that
they cannot on occasion work together.

At the 1376 Parliament, ("the Good Parliament") the Commons,
which formerly had only consented to taxes, took political action
by complaining that the King's councilors had grown rich by war
profiteering at the cost of impoverishing the nation and the
people were too poor to endure any more taxation for the war and
held a hearing on malfeasance of two ministers. The Parliament
found the charges proved and dismissed them from office. This
established the constitutional means for impeachment and removal
of ministers. The commons demanded that its members be elected by
shire citizens rather than appointed by the sheriff. Actions of
this Parliament were undone a few months later.

There was a standard form of direct taxation voted by Parliament,
which was normally 1/10 of the value of all moveables in towns