The Tulip Staircase ghost photograph, Queen's House, Greenwich (1966)

The Queen's House stands in Greenwich, London. Inigo Jones designed it for Anne of Denmark. At its heart turn the Tulip Stairs, which Royal Museums Greenwich calls "the first geometric self-supporting spiral stair in Britain". The ironwork flowers are probably fleurs-de-lis or lilies honouring Queen Henrietta Maria. In 1966 the house was part of the National Maritime Museum.

19 June 1966. A Sunday, about 5 pm. Rev. R. W. Hardy, a retired clergyman from White Rock, British Columbia, was visiting with his wife. They wanted a picture of the staircase. By one account they hoped to recreate a photograph they had seen in a magazine.

The stairs were closed with a rope and a "No Admittance" sign. The couple had already tried to climb them and been turned back. So Hardy shot from behind the barrier. A Zeiss Ikon camera. No flash. Only daylight and the electric candelabra.

Mrs Hardy watched the stairway throughout. "I was free to watch for any possible intrusion during the exposure time," she said. A group of people noticed the preparations, apologised and stepped back. She was certain that "no person or visible object could have intervened without my noticing it." Both of them saw an empty stairway.

The film was developed after the couple returned to Canada. A friend asked who was on the stairs. Hardy was startled. There was a figure. Shrouded. In Peter Underwood's words, it "appeared to be clutching the stairway rail." Royal Museums Greenwich says it appears to be ascending in pursuit of a second and possibly a third figure. Underwood looked closer and found that "both the hands on the stair rail are left hands", each wearing a ring on the marriage finger. To him the pursuing figure had "a distinctly malevolent air."

Several accounts say the film went to the Ghost Club, which passed it to Kodak. Underwood reported that the experts found no trickery or manipulation. Someone, it seemed, had been on the stairs. In 1967 museum photographer Brian Tremain tried to recreate the shot with the Hardys. One account says the attempt was not fully successful.

On the night of Saturday 24 June 1967, seven Ghost Club members held a vigil. Soft-soled shoes. Synchronised watches. Torch, notebook and pencil at all times. They brought still and cine cameras, infrared film, sound recorders and thermometers, and held a séance near the staircase. The museum reports no conclusive evidence of the paranormal. "We did not succeed in scientifically establishing that The Queen's House is or was haunted," Underwood wrote.

No one has formally alleged a hoax. Underwood himself noted that two left hands could point to a double exposure, or to two people. Others suggest a slow exposure catching a moving visitor, a trick of the light, or someone in a blind spot. In 2009 Kimberly Crandell wrote that the picture "is visually confusing until you realize the strange angle at which it was taken". Against all of these stand Mrs Hardy's statement and the rope across the stairs.

Underwood ranked the photograph above the Brown Lady of Raynham Hall. The house has gathered other stories since. On 20 May 2002, gallery assistant Tony Anderson saw a woman in "a white-grey colour, old-fashioned, something like a crinoline-type dress" glide across the balcony and go through the wall. Royal Museums Greenwich still calls the figures on the stairs "a phenomenon that has never been fully explained."