I don't know much about this picture other than it appears to have been taken sometime during the Second World War or shortly thereafter, making it unlikely to be a hoax. My guess is that the ghostly figure at the back of the room was one of the group's comrades who simply refuses to admit that he's dead and sees no reason why he shouldn't be in the picture. Notice that even as a ghost he still wears his uniform.
Borley Rectory | From 1863 until it burned down in 1939, Borley Rectory was considered to be the most haunted house in England. Inhabitants reported seeing the figure of a ghostly nun wandering the grounds, writing would appear on the wall, and servant bells would ring for no reason. When a new family moved into the rectory in 1928, they found a package containing a young woman’s skull. Yikes.16 Terrifying Wikipedia Pages About Ghosts That Will Make You Lose Your Shit
A friend of mine came to my house that night and pointed out what looks to be a woman with her hands folded on her knees in the background, baring in mind the picture was taken facing the living room door. "Although we can't see the face of the figure the rest of it is as clear as day." And Bethany is adamant that there was no one else in the room when the picture was taken: "There was nobody else in the living room at the time, except for the ghost girl in the purple dress."