the king should announce the abolishment of the royal family

That would probably create a constitutional crisis in the UK.

https://en.wikipedia.org/wiki/Royal_prerogative_in_the_United_Kingdom

The power to dissolve parliament is “perhaps the most important residual prerogative exercised personally by the sovereign, and represents the greatest potential for controversy.”[15] This prerogative is normally exercised at the request of the prime minister, either at his or her discretion or following a motion of no confidence. Constitutional theorists have had differing views as to whether a unilateral dissolution of Parliament would be possible today; Sir Ivor Jennings wrote that a dissolution involves “the acquiescence of ministers”, and as such the monarch could not dissolve Parliament without ministerial consent; “if ministers refuse to give such advice, she can do no more than dismiss them”. A. V. Dicey, however, believed that in certain extreme circumstances the monarch could dissolve Parliament single-handedly, on the condition that “an occasion has arisen on which there is fair reason to suppose that the opinion of the House is not the opinion of the electors … A dissolution is allowable, or necessary, whenever the wishes of the legislature are, or may fairly be presumed to be, different from the wishes of the nation.”