Gardiner

Gardiner was an officer aboard the Earth battle cruiser in 2540 which rescued Hardy and Stewart's cargo ship after it had been attacked by Ogrons.

Biography
Gardiner was suspicious of the Third Doctor and Jo's intentions on board the ship. Accordingly, he had them almost immediately placed in the brig, and alerted his superior, General John Williams, about the "stowaways".

He later delivered the Doctor and Jo to a holding cell on Earth, prior to their initial meeting with General Williams and President of Earth Dora. Gardiner offered to get the travellers some food, then advised them to tell the truth quickly to Williams, so as to avoid having the mind probe used on them. (TV: Frontier in Space)

Behind the scenes

 * According to the novelisation, but not confirmed in the televised version, Gardiner's rank is that of captain.