Sam Bishop's great-grandfather

From Tardis Wiki, the free Doctor Who reference

Sam Bishop's great-grandfather was a British Army soldier who fought with the Eighth Army in North Africa during World War II, serving in battlefronts such as El Alamein, Tobruk, and Gazala. Following the war, he would regale the young Sam Bishop with war stories of his time there, inspiring him to eventually join UNIT. (AUDIO: Earthfall, Game Theory, Master of Worlds)