Janus (Bat Attack!)

From Tardis Wiki, the free Doctor Who reference

Not to be confused with the Roman god of the same name.

Professor Janus was an "evil man" with two faces who was apprehended in 1897 by London policeman Inspector Lestrade, with the Tenth Doctor's assistance. He had planned to marry and make "the Case of the Unsuitable Suitor" unsolvable. (DWA: Bat Attack!)