1999s metaphysical approach to science fiction. ITC's New York executives initially rejected the script as it seemed to them to kill off members of the regular cast; it was finally approved for production after Penfold explained the ending. At this point, frustrated at the direction he felt ITC's creative decisions were taking the show, Penfold began to consider leaving the series. The episode incorporated several themes Penfold frequently visited in his work. He felt mankind could be seen as an invading virus, spreading destruction in space akin to the Spanish conquistadores devastation of the New World. It also included anti-war sentiments, his distrust of nuclear technology and the concept of the macro-brain—seen later in "Space Brain". Barry Morse felt it showcased George Bernard Shaw's belief that mankind's worst destructiveness comes either through anger or from fear, which usually prove to be without foundation. Actress Zienia Merton affirms this episode furthered her belief that director Charles Crichton owned significant shares in the company which produced Fuller's earth, the dust-like substance used in films to simulate explosions, create sand- or dust-storms, or age props or costumes. After the dust-storms in the Crichton-helmed "Matter of Life and Death" and "The Last Sunset", the product was mixed with falling debris during the attack on Alpha. Trays were suspended above the Main Mission and Medical Centre sets and tipped onto the cast. Merton avoided the mess by diving under her desk; others, including Martin Landau and Prentis Hancock, were not as fortunate. The alien battleship seen here, designed by Martin Bower, made its debut in the episode "Alpha Child"; it would later appear in "Dragon's Domain" and "The Metamorph". The brain-complex instrumentation was originally constructed for the Kaldorian ship in "Earthbound". The aliens' transparent column-habitats would be re-vamped into growing compartments for "The Troubled Spirit" and other episodes set in Alpha's Hydroponics department. The Hawk spacecraft, also designed by Bower, made its first and only appearance in this story. In response to concerns that it would appear too similar to the Eagles when filmed, Bray Studios technician Cyril Foster hurriedly painted orange details on the miniatures before the shoot. The model was used in a number of visual-effects publicity stills, including some where it can be seen attacking the Bethan gunship from "The Last Enemy". Novelisation The episode was adapted in the fifth Year One Space: 1999 novel Lunar Attack by John Rankine, published in