Page "Royal sign-manual" Paragraph 2

Some letters patent are not signed by the monarch in person.

Instead, the monarch signs a warrant authorizing the preparation of the letters patent ( traditionally written in ceremonial calligraphy on vellum ) and approving the draft text of the letters patent.

Then, once the letters patent are prepared, they are sealed with the Great Seal without the need for the signature of the monarch, because royal authority for issuing the letters patent had already been given by means of the warrant.

Those letters patent finish with the words " By warrant under the Royal Sign Manual ," to signify that they do not bear the sign-manual, having already been approved by warrant.