Battlefield is the first serial of the 26th season of the British science fiction television series Doctor Who, which was first broadcast in four weekly parts on BBC1 from 6 to 27 September 1989. It was the last to feature Nicholas Courtney as Brigadier Lethbridge-Stewart in Doctor Who. In the serial, Morgaine (Jean Marsh), a sorceress from another dimension, summons the planet-devouring Destroyer (Marek Anton) in England, where she also seeks to take the sword Excalibur for herself. The plot is loosely based on Arthurian legend. Part 1's 3.1 million viewers remain the lowest ratings of any full episode of Doctor Who. Plot In response to a distress signal, the Seventh Doctor and Ace materialise the TARDIS near Lake Vortigern in England. At the Gore Crow hotel, they meet a young woman called Shou Yuing and a knight, Ancelyn, who addresses the Doctor as "Merlin". The Doctor shows interest in a scabbard which hangs over the mantelpiece in the hotel. The party is surrounded by an ominous group of knights led by Mordred. When Mordred begins an arcane ritual, the scabbard flies across the room, stirred by the magic. Morgaine then arrives on the scene through a rift in space and time. The next day, archaeologist Peter Warmsly shows the Doctor where he uncovered the scabbard. Under the lake, The Doctor and Ace find a ruined spaceship containing the body of King Arthur, lying next to a sword. When Ace removes the sword from its plinth, she activates a defence mechanism. The Doctor ejects Ace from the spaceship, sending her shooting up through the water and "becoming" the Lady of the Lake. Mordred and Morgaine go to the hotel to retrieve Excalibur. Meanwhile, UNIT troops are staging an evacuation, led by Brigadier Lethbridge-Stewart. Just as Mordred and Ancelyn are about to fight, the Doctor intervenes. Mordred reveals that the battle was a ruse to lure the Doctor, and that Morgaine has summoned the Destroyer of Worlds. The Doctor finds the hotel in ruins, but Ace and Shou Yuing safe. In the debris, the Doctor finds a portal to Morgaine's castle. On arrival, the Brigadier shoots the Destroyer, to no effect. Morgaine releases the Destroyer's bonds; she and Mordred take Excalibur back through the portal. The Brigadier marches back into the castle, tells the Destroyer, "Get off my world!", and empties his revolver (this time loaded with silver bullets) into the