Leo Ryan had an Australian accent, suggesting his country of origin. (TV: The Wheel in Space) By 2000, (TV: The Mind Robber; AUDIO: Prison in Space) 2079 (AUDIO: The Dying Light) or later (PROSE: The Indestructible Man) he was working on the Wheel as a communications officer and had developed a flirtatious relationship with Tanya Lernov (TV: The Wheel in Space) and a friendship with Zoe Heriot. (AUDIO: Last of the Cybermen)
Ryan was excited to destroy Silver Carrier with the x-ray laser and dismissed Gemma Corwyn's concerns before Jamie McCrimmon made his and the Second Doctor's presence aboard the spacecraft known. He was irritated by Zoe's lack of heart regarding the danger the nova of Hercules 208 presented and took over the laser repairs from Bill Duggan, handing some of his normal duties over to Tanya. Following the arrival of the meteorites, Ryan used the repaired laser to destroy them and berated the Doctor for putting Zoe and Jamie in danger by sending them outside of the Wheel and was saddened to hear of Dr Corwyn's death at the hands of the Cybermen.
Eventually, due to Jarvis Bennett's death, Ryan stepped in as the Wheel's acting controller. He and Enrico Casali wrestled Sean Flannigan to the ground upon learning that he was under cyber-control and, once the Cyberman infiltrators were killed, he used the laser to destroy the Cybermen's ship. He then promised Earth Central a full report and held Tanya's hand. (TV: The Wheel in Space)
Weeks later, the Wheel was once again attacked by the Cybermen and Ryan was captured before being subjected to Cyber-conversion. Zoe was able to send the ship into the Land of Fiction where the Cybermen were all destroyed. (AUDIO: Legend of the Cybermen)