M is for... Marshmen

Creatures from the planet Alzarius, located in the pocket universe of E-Space, which have a unique evolutionary history.

Like the mutation which affected the people of Solos, changes in some interconnected Alzarian fauna were closely associated with changes in the decades-long seasons.

For the humanoids who inhabited the Starliner - a spaceship from the planet Terradon which had crashed here many years ago - this atmospheric change was known as "Mistfall". 

A dense mist would rise from the marshes, and the Terradonians would retreat into the Starliner as they believed this to be toxic.

One of the Starliner community's leaders - a triumvirate known as the Deciders - had discovered a secret about Mistfall, and about his own people - a secret which the Doctor later uncovered.

He was present when a number of savage reptilian bipeds emerged from the swamps after the humanoids had fled into their spacecraft.

These creatures adapted very quickly to the atmosphere, and began to master tools. They instinctively made for a cave overlooking the Starliner which had been filled with river-fruits by a group of young Terradonian outsiders. These fruits burst open and spiders emerged. Romana was bitten by one and was transformed into a mental Marsh creature.

The Marshmen brought the TARDIS to the cave, intending to use it as a battering ram to break into the Starliner, but Romana helped them enter through its airlocks instead.

With access to a laboratory and the work of a scientist named Dexeter who was studying the spiders, the Doctor found the same DNA was shared by Marshmen, spiders and the Starliner people.

It transpired that the original humanoids had been killed by Marshmen soon after arriving on Alzarius.

The creatures rapidly evolved into humanoids through exposure to the spider venom. 

The Starliner people were really evolved Marsh people. This cycle had been going on for thousands of years. To break the cycle, the Doctor had the Marshmen leave the Starliner by flooding it with oxygen-rich air, which they couldn't cope with - then had the Deciders finally launch the ship and leave the planet. The Marshmen would then be left to evolve naturally.

Played by: Barney Lawrence, Norman Bacon. Appearances: Full Circle (1981).

• Writer Andrew Smith had originally envisaged the Marshmen as humanoids, like Neanderthals.
• The design is clearly inspired by The Creature from the Black Lagoon.
• Norman Bacon played the "Marshchild". He had previously appeared in Dracula Has Risen From The Grave as the traumatised altar boy, rendered mute after finding a corpse stuffed in the church bell. This impressed Hammer Horror fan Matthew Waterhouse no end.
• Bacon also operated a Dalek in Remembrance of the Daleks, and played one of the rebels in The Sun Makers.
• Lawrence was a regular background artist in the 1980's. He was one of the Kinda hostages in the story of the same name, played Concorde flight attendant Dave Culshaw in Time-Flight, and was one of the Cyberman sentinel androids in Earthshock amongst other roles.