Dear Student,
Ministers have the final say because:
a. Ministers are directly elected by the people.
b. They are answerable and accountable to the people.
c. Democracy is based on the will of the people, who have entrusted responsibility of taking decisions on their elected representatives therefore it is the elected ministers who represents that will and takes the final decision
d. Further, it is the minister who decides the overall objectives on the basis of which policy decisions are made
e. Also that permanent executive that is the civil servants who are experts may hold different opinions regarding varied policies, it is the minister who reaches at a consensus by weighing all the options
Regards