Slater

 was a U.N.I.T. soldier in the late 20th century. He was best friends with McCrae. McCrae and Slater were sexist, often discussing the attractiveness of women in their vicinity, including Romana. They barely survived an attack by a group of daemons from a parellel world. Afterwards, the two seemed quieter and more respectful. (PDA: Heart of TARDIS)