From The Middle Ground by Romerz
Raja Petra explains the Westminster system in greater detail HERE.
And when MB Nizar went to see HRH The Sultan of Perak to request for a dissolution of the assembly, he did so in his capacity as the MB of Perak and by convention of the Westminster system, the Head of State (in this case HRH The Sultan of Perak) should accede to the request even though HRH does have discretionary 'power' empowered by the state constitution.
My understanding of this whole fiasco is that before Najib can announce the formation of a new BN government, he must first remove the existing sitting PR government. As it stands both PR and BN now have 28 seats each with 3 independents claimed to be "BN friendly" by Najib.
Effectively, what we have here is a hung state assembly and unless and until a motion of no confidence is moved in the assembly, the status quo remains! And the status quo is PR is the state government and Nizar is the MB! Because it is a hung assembly, the MB has chosen to face the electorate again and HRH should grant him this request. It is the honorable and right thing to do.
In a sense HRH Sultan of Perak had been put in this unenviable position to safeguard the institution of democracy by UMNO/BN.