You may be looking for Antodus.

Antodus was a member of the Thal expedition to seek another way into the Dalek City via their water supply system. Antodus was frightened of going through the swamp since several Thals had been killed by the mutations there.

Ian Chesterton helped the Thals jump across a chasm in this system to progress by supporting the expedition with a rope tied around him. When it was Antodus' turn to jump, he missed but was fortunately able to cling to the uneven rock face before being pulled up by the others. Ultimately, the party entered the city and joined the others in defeating the Daleks. (NOTVALID: Dr. Who and the Daleks)

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