Bret was born in Mars Colony 16 in the late 40th century. In 3990, he joined the Space Security Service, made First Rank in 3995 and Second Rank in 3998. His sister, Sara Kingdom, also joined the Service. (TV: The Daleks' Master Plan) Bret outranked Sara. (AUDIO: The Guardian of the Solar System)
In 3999, Bret was stationed at the Great Clock. Here he met an older version of Sara who was travelling with the First Doctor and Steven Taylor, where the three of them were caught by Space Security Service, and Sara was brought to him for questioning. Since at the time she was supposed to be on Venus for a six-months assignment, he supposed she had been given a secret mission. She hugged him and started crying when they met, knowing what would happen to him in a few months. He then questioned her, and she, lying, told him she wanted to know about the Clock. Bret then explained to her how the Clock worked, but he was unable to tell her what its function was; for that reason, he had her taken to Mavic Chen, the Guardian of the Solar System, who also happened to be at the Clock. He waited for her audience with Chen to be over and congratulated her when she came out: her audience had been so successful she was to be transferred back to Earth, in Chen's staff. The two brothers waited until the promotion came, and Bret read it, but saw Sara was not happy with it; on the contrary, she started to cry. Having been informed that there was a spacecraft ready to bring her to Earth, Bret left Sara in the hands of his colleagues. He remained perplexed by their meeting, and speculated there could be something more behind her behaviour. Later that day, when the Clock was destroyed, he managed to escape alive and unharmed. (AUDIO: The Guardian of the Solar System)
One year later, he was posted on a mission to the planet Kembel with another agent, Kert Gantry, to investigate the disappearance of fellow agent Marc Cory. Gantry was injured and he forced Bret to leave him so he could have a better chance to escape.
Almost suffering a similar fate to Marc Cory, Bret was saved when he witnessed the arrival of the First Doctor's TARDIS. He waited in the bushes until the Doctor exited to find help for an injured Steven Taylor. Bret then held the Doctor at gunpoint and forced the Doctor to give him the TARDIS key, allowing him to enter the TARDIS. He tried to force Katarina to take him off Kembel, but Steven knocked Bret out. The Doctor returned and placed Bret in a restraining chair and went outside again.
Bret managed to convince Katarina that he would not harm her and gave her two tablets which he said would help cure Steven's blood poisoning. When the tablets worked, Katarina let Bret out of the chair, and he took both of them into the jungle when he saw the Daleks on the TARDIS scanner. He investigated the jungle and saw the Daleks using their flame-throwers to burn down the jungle, after which he returned and warned the Doctor of the danger. The Doctor decided to go to the Daleks' city to find out their plans.
When they entered the city, Bret knocked out Zephon and tied him up. The Doctor donned Zephon's cloak and infiltrated the seventh meeting of the Galactic Council. Bret, Steven and Katarina hijacked the Spar, Mavic Chen's spacecraft. When Zephon sounded the alarm, Bret prepared to take off without the Doctor, but the Doctor managed to get aboard with the stolen taranium core just before they took off.
Bret decided to head to Earth to warn them of the Daleks' plans. The Doctor showed him the tape-recording of Cory's SOS message which he had discovered in the jungle. From the Doctor, Bret learned that Chen had allied himself with the Daleks.
The Daleks used a remote control device to force the Spar to land on the prison planet Desperus. Bret and Steven managed to fix the damaged controls and managed to take off, but one of the convicts, Kirksen, had managed to get onboard and held Katarina captive in the airlock. Kirksen demanded they go back to Kembel or he would kill her. Despite protests from the Doctor and Steven, Bret adamantly refused to turn back. However, Katarina opened the airlock, killing herself and the convict.
Bret managed to land the Spar on Earth and took the Doctor and Steven to a research station run by his friend Daxtar. However, Daxtar gave himself away as a traitor when he mentioned the taranium, which he could not have known about unless he was told by Chen. Angry at Daxtar's betrayal, Bret shot and killed him.
Bret proposed that he could infiltrate the security service and alert the authorities himself. While they were preparing to leave, Bret's sister Sara entered. Sara, who had been convinced by Chen that Bret, the Doctor and Steven were traitors, held them all at gunpoint. However, Bret managed to cause enough of a distraction to allow the Doctor and Steven to escape but was then shot and killed by Sara. Once Sara learned the truth, she allied herself with the Doctor to save Earth and avenge Bret's death. (TV: The Daleks' Master Plan)
On the Space Security Service Station 7, the Eleventh Doctor told Tranter that he had worked with Bret Vyon and Sara Kingdom, prompting the station commander to comment that he had impressive credentials and must have started fighting the Daleks at a very young age. (COMIC: The Only Good Dalek)