Heard: The Enemy of the World by PatriTroughton, et al. From the 1967 TV broadcast, 2002 (by BBC Audiobooks).
Another multi arc episode from Dr. Who with narration to describe action. Troughton played Dr. Who and I'm not going to look up the script writers. The internet said the shows aired in 1968.
The Dr., Jaime and Victoria land the Tardis on a beach. The Dr. is excited to play in the surf and sand. The are spotted by some men in a hovercraft. The hovercraft men see the Dr., call a woman named Astrid and claim "He's here!" The men and Astrid argue and the men set out to kill the Dr. The Dr. and companions head for the sand dunes and are rescued by a helicopter flying Astrid.
Astrid explains that the Dr. is a dead-ringer for Salamander. Salamander is a ruthless and rising star in the world government. Salamander seems able to predict natural disasters and prevent destruction. salamander's agricultural work is feeding millions. People love Salamander. Salamander is politcally strong. Astrid is working with Giles Kent to reveal Salamander's evil doings. They try to convince the Dr. to impersonate Salamander to get evidence.
Things happen. The Dr. impersonates Salamander. Many close calls with the cops after the Dr. and Astrid's group. Salamander engineers a sneaky coup against the government leaders in central Europe. Salamander sneaks underground where a group of scientists have squirreled away after Salamander told the a nuclear war has left the surface with deadly radiation. Salamander has the scientists create volcanic eruptions, earthquakes, etc. to stop the war mad survivors on the surface.
More things happen. There are show downs. Salamander finds his way into the Tardis but is flung outside when the Tardis takes off and the door is open.
1. Kind of a sudden ending. The Tardis lands, the Dr. says "watch for [something]" and lots of shooting noises erupt.
EDIT, 13 November 2013:
1. I was looking again to see if there is any online video. This story arc was incomplete for years until film of a missing episode was found in Nigeria, the story compiled and released for sale online.
2. The Onion has a write-up on the story. The writer is obviously a big-time Who fan.
3. The story itself is a reflection of the mid-'60s love for spy stories.