Only a few years from now, a squad of UNIT troops is escorting a nuclear missile through the English countryside. At the nearby archaeological dig, knights in armour are fighting battles with broadswords – and guns and grenades.

The Doctor arrives on the scene and meets two old friends: Brigadier Lethbridge Stewart, called out of retirement to help in an emergency, and Bessie the souped-up roadster.

Ace escapes from death by drowning in a submerged spaceship, only to find herself at the mercy of a demon known as the Destroyer.

The action is fast and furious, as expected in a script by Ben Aaronovitch, who wrote the classic Remembrance of the Daleks. And why do the knights address the Doctor as 'Merlin'? What is the power of the sword that Ace retrieves from the bottom of the lake? Will Morgaine carry out her threat to destroy the world?

This novelization is by Marc Platt, who both scripted and novelized Ghost Light, the story that immediately followed Battlefield in the 1989 season.