Leo Ryan was a communications officer on Space Station W3 in 2079. He traced the Silver Carrier as it approached the station.
He told Zoe Heriot she was "just like a robot". He was angry at the Second Doctor for sending Zoe with Jamie McCrimmon to the Silver Carrier.
He helped the Doctor defeat the Cybermen. (TV: The Wheel in Space)
During a second attack on the space station by the Cybermen, he was captured and underwent cyber-conversion. (AUDIO: Legend of the Cybermen)