The Tenth Planet of malevolent cyborgs that became a recurring adversary in later "Doctor Who" stories. The "tenth planet" in the title makes reference to a fictional lost planet in Earth's Solar System; at the time of production, the Solar System was generally held to consist of nine planets, prior to the redesignation of Pluto as a minor planet. "The Tenth Planet" is an incomplete "Doctor Who" serial – one of many serials that were affected by the BBC's policy of wiping archived programmes in the 1960s and 70s. Only three of the four episodes are currently held in the BBC archives; the
Gustav Holst horrors". Nevertheless, the composer and critic Colin Matthews recognises even in these apprentice works an "instinctive orchestral flair". Of the few pieces from this period which demonstrate some originality, Matthews pinpoints the G minor String Trio of 1894 (unperformed until 1974) as the first underivative work produced by Holst. Matthews and Imogen Holst each highlight the "Elegy" movement in "The Cotswold Symphony" (1899–1900) as among the more accomplished of the apprentice works, and Imogen discerns glimpses of her father's real self in the 1899 "Suite de ballet" and the "Ave Maria" of 1900. She and Matthews have asserted that Holst