Sam Bishop

 was a member of UNIT.

Early life
Though he came from a family of bookkeepers and teachers, Sam was inspired to join the British Army as a child by his great-grandfather, who would regale him with stories of when he fought with the Eighth Army in North Africa during World War II, serving in battlefronts such as El Alamein, Tobruk, and Gazala. (AUDIO: Earthfall)

Stopping a Nestene invasion
With UNIT, Bishop often went on dangerous missions. Kate Stewart sent him on a mission to the Gobi Desert to track a Nestene energy units. On this mission, a group of Autons attacked him. He was then sent to Puerto Rico to track the energy units landing. (AUDIO: Earthfall)

He sent Kate and Colonel Shindi to Black Archive 5, as there was something useful in the vault. (AUDIO: Armageddon)

Tengobushi Incident
When he came back to the United Kingdom, he was supposed to meet with Kate Stewart but he missed her as she was on her way to Geneva. He helped Josh to realise that the Tengobushi killed Anna Burges to get information on where Osgood was going. (AUDIO: Death in Geneva)

On Kate's orders, he followed Felicity Lyme to Antarctica and discovered her facility in there which was generating enough electricity to supply the British Isles. He posed as a man from an energy company to find this information. He managed to get the other territorial powers on the continent to show a force of strength against Bergam's forces. (AUDIO: Ice Station Alpha)

Investigating the Silence
He thought that Kenneth LeBlanc was idiotic. After hearing both Kate and Osgood's memories about the incident at Helena Faversham, he decided to investigate further. He looked at the CCTV footage of the raid and convinced Kate that it had happened. He then helped Osgood to investigate the people who McGee said had visited the house. (AUDIO: Square One)

He had to deputise for Carter when he went AWOL. He found the footage in the Apollo 11 moon landing telling the humans to kill the Silents on sight. He then went with Osgood to find out where Carter had sent a set of explosives. Going with Kate and Osgood to LeBlanc constituency count, he took a set of troops to destroy the Silents there and disarm a bomb. (AUDIO: Silent Majority)

He went with Osgood to the UNIT satellite to fix something there, but they were knocked unconscious upon arrival. He explored the space station and discovered that the crew had been killed. Due to the Silents editing his memory, he forgot this and aided Osgood in finishing her mission. He decided to get Osgood and himself off the station piloting the Suez capsule. (AUDIO: In Memory Alone)

The Silurian invasion
He was called in to help Kate and Osgood in a Silurian nest in Greece. Finding the Kate injured he gave her some anti-venom to try and save her. He eventually found Osgood in a primitive state. Tryska started to attack him in a weapon testing area of the base. He was annoyed that Tryska decided to fall into a hole. Later she appeared and with Osgood's suggestion placed a snake calling device on her. Josh then evacuated them from the area. (AUDIO: Retrieval)

Kate later sent Sam to a weather station in order to affect the weather, changing the Gulf Stream to make it snow, so that Kate could get back to the UK. He went back to the Sea Devil base with Jo Jones to take the sea creatures that the Silurians were using back into hibernation. (AUDIO: United)

Sam Goes Missing
Sam provided the intelligence about a local resistance force in South America had obtained alien technology. (AUDIO: The Dalek Transaction)

After this, he disappeared for some time although Kate wasn't overly concerned. (AUDIO: The Sontaran Project)

Eventually he did get back in contact with more information on the auctioneers and their worldwide network. (AUDIO: False Negative)