Douglas Caldwell

Douglas Caldwell met Gerald Kneale in 1908 when he was a draughtsman in the Royal Engineers. He helped Carter when the Z127 zeppelin became ensnared in the Rift. It wasn't until the war broke out in 1914, however, that Gerald decided Douglas' talents would be better applied within Torchwood Three. He was loyal to Torchwood for many years and in 1930 transferred to Torchwood One to work in R&D where he was instrumental in cloaking technology. He died in 1957. (TV: To the Last Man)

Behind the scenes
The full version of the photograph seen in the episode was released by the production team in The Torchwood Archives.