Chester tour guide Mary Ann Cameron posted the picture on her Twitter feed after one of the visitors in her group showed her the photo a few nights ago.
Mary, who launched her book Chester City of Ghosts at St John’s Church in 2015 dressed as a ghoul, tweeted: “Was the ghost of the lady in white roaming Dee House with her light last night? Photos taken by one of group last night!”
She later posed the question: “A rare sighting or will she appear during the next ghost tours?”
Dee 106.3’s Gavin Matthews, who was copied in on the conversation, responded: “A mystery!..”
Chester businessman Adam Dandy magnified the picture and joked: “If you zoom right in.... she’s pretty hot!
On a serious note, he hopes the apparent light at the window in not a sign someone is sleeping rough inside the derelict and potentially dangerous building.
One website says of the resident Dee House ghost: “Apparition of old woman sometimes seen prowling top floor of this old telephone exchange and onetime convent.”
Dee House is a grade II-listed Georgian building built in about 1730 as a town house for John Comberbach, a former mayor of Chester.
It continued in use as a private residence until about 1850, when it was sold to the Church of England. In 1854 it passed to the Faithful Companions of Jesus, a religious institute of the Roman Catholic Church, who used it as a convent school. They added a wing to the east, which incorporated in its ground floor a chapel designed by Edmund Kirby.
In 1925 the building was taken over by the Ursulines, another religious institute. In 1929 they added another block to the south of the building, and during the process the remains of a Roman amphitheatre were found beneath it.
In the early 1970s the convent closed and the building was used as offices by British Telecom. They vacated the building in the early 1990s and it has been empty since.
Last year Cheshire West and Chester Council revealed Daniel Thwaites Plc was the successful bidder in a contest to redevelop the crumbling building. Plans were unveiled to transform it into a hotel, restaurant and interpretation area for the amphitheatre but progress has been slow.
■ Anyone wishing to join Mary Ann Cameron on a Chester ghost tour, which runs every Friday and Saturday, can book through the website.