Nathan (A Fix with Sontarans)

Group Marshal Nathan of the Tenth Sontaran Battle Brigade was one of two Sontarans who planned to destroy the Sixth Doctor's TARDIS with a vitrox bomb. He had a subordinate who served under him.

Biograpy
Inexplicably, both Group Marshal Nathan and the unnamed Sontaran subordinate managed to board the Sixth Doctor's TARDIS with a vitrox bomb, plotting to blow up the TARDIS as soon as they fuelled the bomb by connecting it to the main power cable, but, the Doctor anticipated this, and with an accidentally teleported Tegan, they isolated the power to the control room to lure the duo to them. After Tegan accidentally teleported Gareth Jenkins to them, they laid a trap for Nathan and the unnamed Sontaran.

Upon arriving, the Doctor shouted at Group Marshal Nathan, and the unnamed Sontaran told the Doctor to speak to Nathan with respect. After the Doctor identified Tegan and Gareth to the Sontarans, Nathan spoke to the unnamed Sontaran about the unexpected prize they'd captured, as they knew of a Gareth Jenkins from the Earth Defence Force in the future who thwarted a future invasion of Earth. However, after Nathan instructed the unnamed Sontaran to kill Gareth, Gareth unleashed the trap, which shot gas at the Sontarans, brutally killing them. (HOMEVID: A Fix with Sontarans)

Tegan later recalled the duo of Sontarans when talking about the adventure with the Sixth Doctor in Heathrow Airport. (PROSE: Fixing a Hole)

Behind the scenes

 * Group Marshal Nathan and his subordinate, unnamed on-screen but referred to as "Turner" in the script, were a sly reference to the then-current Doctor Who producer John Nathan-Turner. This happened in rehearsal: the script called him Group Marshal Stern. (DWM 104)
 * In Doctor Whoah! 383, the Sontarans from The Two Doctors (Stike and Varl) get angry at their agent for not getting them roles since A Fix with Sontarans; this implies that Stike is Nathan and Varl is Turner, which makes sense considering the costumes and actors were reused from The Two Doctors for A Fix with Sontarans.