Gareth Jenkins (in-universe)

Gareth Jenkins was a young child from 20th century Earth who helped the Sixth Doctor defeat a duo of Sontarans. Gareth claimed that, prior to this encounter, he had enjoyed renditions of the Doctor's adventures on televsion.

Gareth Jenkins may have been the leader of the Earth Defence Force by the 21st century, thwarting the Sontarans' invasion of Earth in 2001.

Biography
Prior to meeting the Sixth Doctor, Gareth watched a series about the Doctor on television that taught Gareth the various controls on the TARDIS control console. He also obtained a costume of the Sixth Doctor's usual attire. (HOMEVID: A Fix with Sontarans)

On 23 February 1985, (PROSE: Fixing a Hole) as the Doctor was trying to stop a duo of Sontarans, Group Marshal Nathan and his subordinate, from blowing up the TARDIS with a powerful vitrox bomb, he accidentally teleported his former companion Tegan onto the TARDIS. As they set about isolating the power to the TARDIS control room to lure the duo of Sontarans to them, Tegan accidentally teleported Gareth to them after pressing the wrong button on the control console.

While the Doctor was reluctant to have Gareth help as he doubted a mere human could do anything if a Time Lord couldn't, he let Gareth help him set a lethal trap for the Sontarans. After the duo of Sontarans arrived, they recognised the name of Gareth as belonging to the leader of the Earth Defence Force in the year 2001 who thwarted their future invasion, and Nathan was happy about what a prize he captured. He instructed his subordinate to kill Gareth to ensure that the future invasion would be successful, and while the Doctor suggested that their names may just be a coincidence, it was not a risk Group Marshal Nathan was willing to take; faced with no other choice, the Doctor told Gareth to unleash the trap they had set up, releasing gas that brutally killed the duo. Tegan and the Doctor congratulated Gareth, the victory was short lived, as Tegan pointed out that the TARDIS scanner had turned on, revealing a fleet of ships from the Tenth Sontaran Battle Brigade, and the Doctor told Gareth "this is only the beginning!" (HOMEVID: A Fix with Sontarans)

Within the space of a few hours, the Doctor returned Gareth to his correct time-stream.

When the Doctor returned Tegan to Earth, not knowing he had finally reached Heathrow Airport due to the time-alignment field being damaged and the TARDIS scanner simply showing a white haze, set about exploring the snowy outside with Tegan as the TARDIS needed to repair, shutting down the oxygen supply. When they began talking as the walked, Tegan recalled her reunion like a flashback in a film, imagining that if the reunion was a comedy, then Gareth's comic belittling of the Doctor would've been accompanied by comedy stings of incidental music. (PROSE: Fixing a Hole)

Personality
If the Sixth Doctor was correct in his assumption that Gareth was like himself, then Gareth would embody traits of courage, intellect, and perspicacity. Gareth also seemed to be fairly reserved, although he did have fun in making the Doctor and Tegan jump. (HOMEVID: A Fix with Sontarans)

Behind the scenes
Gareth Jenkins, who lived in Milton Keynes, wrote into the wish-fulfilment programme Jim'll Fix It in around 1985, to ask if he could meet Colin Baker and go inside the TARDIS; his request was approved, and A Fix with Sontarans was formed, a mini-episode wherein Gareth got to do just what he asked.

However, after the death of Jimmy Savile in 2011, the individal who hosted Jim'll Fix It, was exposed as a serial paedophile , and A Fix with Sontarans was removed from later pressings of the DVD release of The Two Doctors, which had included it since the DVD's original 2003 release. However, it was clarified by Jenkins himself that Savile had not taken an interest in him. In 2022, the Doctor Who: The Collection — Season 22 blu-ray boxset was released, including a newly-recut edition of A Fix with Sontarans, which entirely removed two minutes of footage of Savile, replacing it with a new CG scene with ADR as a new ending to the story.

As the original version of A Fix with Sontarans broke the fourth wall so thoroughly — essentially dissolving into the real world — this Wiki never considered it a valid source for writing "in-universe" articles with. It was only in coverage of PROSE: Fixing a Hole — a short story that acted as a sequel to A Fix with Sontarans and as the the thematic and conceptual concluding bookend to Tegan's journey with the Doctor — did references come to A Fix with Sontarns in valid media, albeit vaguely. FIxing a Hole notably ignored the ending of the original A Fix with Sontarans, long prior to the crimes commited by Savile came to public attention. The 2022 recut edition, as it omitted the original fourth wall breaking ending, is a valid source, however due to the ending being changed, the references to Gareth's Nan and the naming of the meson gun remain in the orignal, and thus, as invalid source articles.

Information from invalid sources
According to one account, after eight year old Gareth killed Nathan and the subordinate Sontaran, Jimmy Savile entered the TARDIS, asking the Doctor if "[Gareth] passed the test". After the Doctor confirmed so, Savile asked Gareth where he got his coat, and Gareth told him that his Nan made it for him. Savile asked the Doctor to place a Jim'll Fix It medal over Gareth's bonce, and as the Doctor did so, he told Gareth that he was "well and truly fixed." (NOTVALID: A Fix with Sontarans)