Gavrok is the main antagonist of the Doctor Who story "Delta and the Bannermen".
He was portrayed by the late Don Henderson, who also portrayed General Tagge in Star Wars: A New Hope.
Gavrok was the leader of the Bannermen, who he led in a genocidal war against the Chimerons. His campaign managed to wipe out the entire Chimeron race aside from their queen, Delta, who fled the planet in a stolen spacecraft, taking with her one of her people's eggs. Gavrok pursued her to a spaceport but arrived too late to stop her leaving on a tourist bus. Gavrok interrogated the Tollmaster, who explained the bus was meant to be travelling to 1959 Disneyland but had been knocked off course by a collision with an early satellite. Satisfied he knew nothing more, Gavrok told the Tollmaster he was free to go... and then shot him in the back as he walked away.
Gavrok sent out an alert promising a bounty for news of Delta's location. The call was answered by a bounty hunter named Keillor, who reported that Delta was at a holiday camp, Shangri-La, in Wales. After getting a fix on the tracking device, Keillor had set up, Gavrok detonated it remotely, killing the bounty hunter. His spacecraft landed near the location: The first people the Bannermen encountered were Hawk and Weismuller, two American agents looking for the satellite, who he had taken prisoner and kept under guard in the field.
Attacking the holiday camp, Gavrok blew up the tourist ship as it was about to leave, killing everyone on board. He was momentarily convinced by Mel that Delta had been on board and celebrated the end of his campaign, until he saw Delta fleeing the scene with the Doctor and others. He was convinced by camp manager Burton to spare him and Mel in order to use them as hostages...or, as Gavrok preferred, bait. When the Doctor arrived to parlay, Gavrok casually shot away his white flag but allowed him to take Mel and Burton and leave. He had a tracking device attached to their vehicle, hoping they would lead him to Delta, and also placed an electrified force field around the TARDIS to stop them leaving that way.
The Doctor dumped the tracking device in a field. Callon, one of the Bannermen left guarding Hawk and Weismuller, arrived in a disheveled state: Gavrok nearly killed him on sight but spared him when he revealed he knew where Delta was. However, the Doctor's group had already left the cottage where Callon had seen them, leaving behind a trap that resulted in the Bannermen being attacked by bees.
Gavrok realized the group had returned to the holiday camp and prepared to attack, ordering his men to kill everyone except the Chimeron princess (who had hatched from the egg) who he wanted to kill himself. However, the Doctor had rigged up the camp's PR system to broadcast the Chimeron princess' ultrasonic scream. The Bannermen were left disorientated by the noise and Gavrok ended up stumbling into the force field around the TARDIS and being disintegrated.