'Battlefield' (4 Parts) Story Code '7N' by Ben Aaronovitch

The Doctor receives a distress call, and materialises the TARDIS in Carbury on Earth, where he and Ace find that a nuclear missile convoy, in the charge of UNIT's Brigadier Winifred Bambera, has become stuck near lake Vortigern. The Doctor and Ace meet Peter Walmsley, the manager of the Carbury Trust Conservation area, who tells them that the lake is believed to be the final resting place of King Arthur and his sword Excalibur. He takes the two travellers to the Gore Crow Inn, where Ace befriends a Chinese girl named Shou Yuing. Meanwhile, Ancelyn, a knight from another dimension, arrives on Earth to recover Excalibur, but the evil knight Mordred follows him. They both recognise the Doctor as Merlin, who is revealed to be one of the Time Lord's future incarnations. Hearing of the Doctor's return, Brigadier Lethbridge Stewart is ordered out of retirement to come to the aid of UNIT. After a battle breaks out between Mordred's troops and those of UNIT, Mordred summons his mother, the powerful sorceress Morgaine. The Doctor and Ace discover that under the lake lies an extra-dimensional spaceship containing the body of King Arthur held in suspended animation, and Excalibur. Ace takes the sword, and returns to the Gore Crow Inn. Morgaine is unable to seize the sword as Ace and Shou Yuing have protected themselves with a chalk circle. The sorceress summons the Destroyer, a powerful blue-skinned demon, who helps her to gain control of the sword. The Doctor and the Brigadier confront Morgaine and the Destroyer, and the Brigadier uses silver bullets to kill the demon. Morgaine escapes, and reunites with Mordred. Ace and the Doctor return the sword to the safety of the space ship, where the Doctor discovers that Arthur's suit of armour is in fact empty; a note from his future self explains that the king died in battle. Morgain gains control of the nuclear missile, and plans to detonate it, but the Doctor convinces her that there is no honour in such a victory, and she gives herself up. UNIT takes Morgaine and Mordred into custody.

Sylvester McCoy (The Doctor), Sophie Aldred (Ace), Jean Marsh (Morgaine), Nicholas Courtney (Brigadier Lethbridge-Stewart), James Ellis (Peter Warmsly), Angela Bruce (Brigadier Winifred Bambera), Christopher Bowen (Mordred), Marcus Gilbert (Ancelyn), Angela Douglas (Doris), Noel Collins (Pat Rawlinson), June Bland (Elizabeth Rawlinson), Ling Tai (Shou Yuing), Robert Jezek (Sergeant Zbrigniev), Dorota Rae (Flight Lieutenant Lavel), Stefan Schwartz (Knight Commander), Paul Tomany (Major Husak), Marek Anton (The Destroyer)

Produced by John Nathan-Turner
Directed by Michael Kerrigan

TX:
Part 1 - 6th September, 1989 @ 7.35pm - 8.00pm
Part 2 - 13th September, 1989 @ 7.35pm - 8.00pm
Part 3 - 20th September, 1989 @ 7.35pm - 8.00pm
Part 4 - 27th September, 1989 @ 7.35pm - 8.00pm

Notes:
*Featuring the Seventh Doctor, Ace, Brigadier Lethbridge-Stewart and UNIT, and introducing Brigadier Winifred Bambera

*Working titles: 'Storm Over Avallion', 'Storms Over Avallion'