The fact that the Prime Minister, in the "Westminster" system and its colonial derivatives, decides the date of elections is nothing other than a carry-over from royal prerogative, as you demonstrate, Gary. It is quite unjustifiable in the current political climate, because it arbitrarily accords this vital attribute of sovereignty to a mere chief of government.

As there is no prospect of handing this power back to the constitutional head of state, nor any realistic prospect of vesting it in an elected head of state, a fixed-term parliament is the only tenable position.

The vital question in a democracy is : does the government have the confidence of Parliament?  Arbitrary dissolution turns this question on its head.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}