C16S05 The power of Kroll

Synopsis

Searching for the fifth segment of the Key to Time, the tracer brings the TARDIS to treacherous swamps on the third moon of the planet Delta Magna.  The Doctor and Romana soon uncover a plot to wipe out the Swampies, the local inhabitants, by the duplicitous crew of a gas refinery.

Meanwhile, a massive creature is stirring beneath the waters, and the primitive Swampies believe the only way to clam the powerful monster is human sacrifice...

Cover notes

As part of his brief, writer Robert Holmes was asked to come up with the biggest monster ever to appear in Doctor Who.  He didn't think this was a particularly good idea, but delivered a four-part script featuring a monster called Kroll — a tentacled creature that had swallowed the fifth segment of the Key to Time.  And yes, the Kroll monster is certainly huge...

Filmed around the River Alde new Aldeburgh in Suffolk, the eerie marshes are particularly effective.  Location filming was more extensive than normal for a four-episode story — with nine days allocated for all the exterior scenes.  The shoot proved difficult at times due to the tidal nature of the marshland.  Water levels would rise during takes and at one point Tom Baker and Mary Tamm became stuck in the marshy ground, resulting in Mary losing one of her shoes!

The swamp setting wasn't particularly robot-dog friendly, so K-9 was written out for these episodes.  However, when the actor who was originally going to play the part of Dugeen dropped out, John Leeson, who normally played the voice of the metal mutt, got his chance to appear in front of the cameras for the first time in Doctor Who.

Although one of the less inventive stories in the Key to Time sequence, The Power of Kroll must have resonated with its author — he would re-use elements of the story to rather more thrilling effect for Peter Davison's swan-song The Caves of Androzani six years later...

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