What he has the power to do.

Technically he only has the power to authorise. The PM has the power to request.

When the reformation happened. After beheading the last ruling king. It became a little more complex then the king passing soverignty to parliment. As the king did not have soverinty after the covil war.

Post reformation when parliment is xlosed. The king is authorising the government (IE pm) to gain sovereignty from parliment. But parliment must actually pass it.

So power never actually resodes in the king under the post reformation constitution. But is passed between parliment and the PM. Hence why the Government \PM is innpower during an election cycle.

The only way the ki g could force parliment to disband. Would be to try and retake power using the loyalty of paliment or the military (who rechnically still swear to obay him).

But technically he dose not have the power to force it legally.