Torchwood Four
From Tardis Wiki, the free Doctor Who reference
Torchwood 4 was a branch of the Torchwood Institute. The nature of this branch and its personnel where unknown. The Torchwood Archives tell of Torchwood 4 being under a golf course in Inverness. According to information passed from Torchwood 3 operative Jack Harkness to new recruit Gwen Cooper, Torchwood 4 he told her it was lost, though there was hope it would be found one day. (TW: Everything Changes)
Fan Films[1]have suggested that other Torchwood bases exist in one or more of the Commonwealth countries, citing Toronto's CN Tower as the base for Torchwood 4.
