Alex Klein
From Tardis Wiki, the free Doctor Who reference
Alex was the senior aide to Harriet Jones in Downing Street in 2006. He was with her when she was teleported aboard the Sycorax ship. He acted as a translator until the Doctor's TARDIS resumed its translation.
After giving Torchwood One Jone's permission to murder the Sycorax, the Tenth Doctor whispered to Alex, "Don't you think she looks tired?" — six words that began a chain of events leading to Harriet Jone's downfall. (TV: The Christmas Invasion)