was a pilot who flew into the Cardiff Rift
. She was the lover of a married man prior to going through the Rift.
On 18 December 1953, she, John Ellis and Emma-Louise Cowell were on their way to Dublin in Diane's plane, the Sky Gypsy, when it flew through the Cardiff Rift and ended up in Cardiff more than 50 years later.
Diane and Owen Harper had a relationship, but she decided to fly away and try to find the Rift again, to get back to 1953. (TV: Out of Time)
Owen activated Torchwood Three's rift manipulator with the intent of forcing the Cardiff Rift back open, hoping to find Diane again. Ianto Jones tried to stop him, but failed after a violent scuffle. (TV: Captain Jack Harkness)
Later, an apparition claiming to be Diane appeared to Owen after he opened the Rift. This was later revealed to have been a vision caused by Bilis Manger. (TV: End of Days)