Gavrok

Gavrok was the leader of the criminal organisation, the Bannermen.

Searching for Delta
Led by Gavrok, the Bannermen attacked the Chimeron home planet, Chumeria, intending to wipe the Chimerons out. However one Chimeron, Delta, escaped and fled in a Bannerman craft. Gavrok and the Bannermen followed her to a toll port where they interrogated the Tollmaster as to her location. When he proved unable to provide the information Gavrok killed him. A mercenary informed Gavrok of the whereabouts of Delta, Shangri-La camp, Earth. Gavrok used a high-impulse beam to kill the mercenary so he didn’t have to pay him.

On Earth
However he had killed him too early, Delta's exact location was unknown so Gavrok ordered a scan of the area for high technology. They found her and landed, taking Jerome Weismuller and Hawk prisoner. Gavrok ordered two Bannermen to guard the prisoners whilst he and the rest moved on to the camp. They arrived in time to destroy the Nostalgia Tours bus, Gavrok confronted Melanie Bush, the only survivor and inquired if Delta was aboard. She lied telling him she was. However moments later Delta passed on a motorcycle. Gavrok decided to use Mel and the camp leader Burton as bait. The Doctor approached the Bannermen under the white flag but Gavrok merely shot it, the Doctor then informed Gavrok he had to let Mel and Burton go as he was already in enough trouble from his law breaking. He let them go and signalled the Bannermen guarding Weismuller and Hawk to place a tracker on the bike, meanwhile he booby trapped the Doctor's TARDIS with a sonic cone. He then followed the signal to a dead end but one of the guards informed him of where Delta's hideout was. He arrived and walked into a trap. Gavrok and the Bannermen were covered in Honey attracting Goronwy's bee's to attack them. He reorganised and set out for the camp, the sound of the Chimeron Princess was amplified through a stereo sending Gavrok and the Bannermen into disarray. Stumbling, Gavrok fell within the perimeter of the sonic cone and was atomised. (DW: Delta and the Bannermen)

Personality
Gavrok led the Bannermen with the intent to wipe out every Chimeron. He was merciless in his gunning down of Chimerons when he invaded. He told the Tollmaster he was free to go and then killed him as he turned away. He had little respect for convention, firing upon the Doctor whilst he was under the flag of truce. (DW: Delta and the Bannermen)