The monarchy's power began to decline during the reign of George III. Although they technically kept all their powers, they lost the system of patronage that allowed them actually use them. During the reign of George III no Prime Minister he ever appointed lost an election or a major vote in parliament. Because of the extensive system of offfices the monarch appointed on his own, it ensured it paid to back the Kings choice. The term office for profit under the crown still had a very literal meaning back them. Pitt the younger, in order to create more effective government, streadly removed these offcies froim crown appointment and moved them over to a system of merit based appoitnment (although having the right connections didn't do you any harm). So although Victoria (and all sucessors) could technically refuse to sign any bill they didn't like, they never did. The reign of Victoria is the start of the modern monarchy.