Hallan

Hallanoberen, commonly known as Hallan, served as Commander and personal bodyguard to many Lord Presidents of Gallifrey. He was privately very conservative and thus he disapproved of many of President Romana's reforms. (AUDIO: Imperiatrix)

On one occasion, Hallan informed Cardinal Irving Braxiatel that Inquisitor Darkel wanted to meet with him. (AUDIO: The Crystal of Cantus)

He accompanied Romana and Leela to the holiday world of Davidia — he had been there many times and knew the staff well. One of them, Melyin, tricked him into a compromising embrace to get her contract terminated. By this point, he had been working on escort duties for 700 years and had already visited Davidia forty-two times. (AUDIO: Spirit)

When a bomb in the Scapheports started its detonation sequence, he closed the bulkheads to stop the explosion propagating too far, killing many alien students and destroying K9 Mark I in the process. He did this to protect Romana, Leela and other Time Lords. At first, he supported Darkel's challenge to Romana's authority; but, in the ensuing election, Hallan sided surprisingly with Romana when she declared herself Imperiatrix and arrested Darkel and the High Council. (AUDIO: Imperiatrix)

After the appearance of Pandora, the first female president of Gallifrey returned in the form of Romana's first incarnation, and Pandora's assumption of power, Romana's second incarnation was freed from her cell by Hallan's guards. He became the military leader of the resistance to Pandora. Having destroyed the means of using any TARDISes, Hallan and Romana escaped the city and made their way to the Celestial Intervention Agency's Anomaly Vaults to retrieve the one functioning TARDIS on Gallifrey and secretly return to the destroyed Time Lord Academy. Whilst Hallan led the resistance inside the city, Matthias contacted Darkel and gave an infected disc from her to Hallan, who was infected and had to enter stasis until a cure could be found. (AUDIO: Fractures, AUDIO: Warfare)

Behind the scenes
Although the full name "Hallanoberen" comes from the Big Finish Productions audio story Warfare, its actual spelling is pure conjecture.