In an alternate timeline, Captain John Hart took control of the British Empire and the Torchwood Institute, having deliberately changed the course of history in a bid to steal the life of his former partner Jack Harkness. (AUDIO: The Death of Captain Jack)
Through use of a Rift Manipulator, John siphoned off Jack's immortality, transferring it to himself and imprisoning Jack on the island of Flat Holm. Taking charge of the Torchwood Institute, John used the technology to re-establish the British Empire under his rule.
In the 20th century, John faked the spaceship crash at Roswell, New Mexico using a fake spaceship Torchwood had built and a couple dwarves he had dressed as aliens. He confided to Norton Folgate that he did this because he was bored as there was "nothing on the telly.
In the 21st century, John hired Ianto Jones as his personal assistant, making him dress in bondage-themed outfits and torturing him for fun. Informed by Yvonne Hartman of the discovery of the Sphere, John ordered that it be opened despite the reservations of Doctor Rajesh Singh. This resulted in the release of the Sphere's Dalek occupants who proceeded to massacre Torchwood One and the home counties.
At Torchwood Cardiff, John was responsible for the deaths of Toshiko Sato and Gwen Cooper during Torchwood missions, considering their lives expendable. He murdered Rhys Williams to keep him from going to the media, having Owen Harper dispose of the body with an incinerator.
Later, an alien ambassador came to Earth and asked for 10% of the world's children, a request which John had no issue in accepting. Later still, John was introduced to the Blessing, which he commented as looking like "a giant arse."
Ultimately, this version of the universe came to an end in 2017, 130 years following John's arrival. Receiving word that Jack was dying, John visited Flat Holm to see him in his final hours. After gloating to Jack of how he had changed the course of history and stole his life, John was confronted with a truth that he knew, that the universe was dying as time and space contracted, a result of John robbing Jack of his immortality and thus tampering with a fixed point in time. John had in fact visited Jack to find a way to stop the end of the universe only for Jack to tell him that he was taking what he had stolen back; John was never meant to have his power, becoming a "warped reflection" whose domain was now a dying universe cut off from reality. It was at this point that Jack finally died, after which John discovered that everyone apart from himself had disappeared. Finding himself alone in a collapsing universe of his own making, John cried to Jack that he was sorry as his reality was negated. Meanwhile, as Jack put it, everything went back to "how it should be." (AUDIO: The Death of Captain Jack)