Some mourners had queued for 11 hours to sign the books of condolence. A few felt they got more than they had bargained for. "Are you the press? I have to tell you something," said one hysterical woman. "At the end of that hall there's a painting. The light is shining on that painting in a particular way and Princess Diana's face is looking out of it. Everybody's seeing her face looking out."
A sober-looking man in a suit leapt to her defence. "There's something in that. I don't know what the heck it was. This lady started and I thought: 'Oh my God, she's mad. She's lost the plot.' It's quite a shadowy face in the top right-hand corner of the painting. I'm not going to say it's Princess Diana, but it's something very strange and it did shock me. I swear to God - and I'm not some nutter."
David Bennett, 32, a restaurateur from Winchester, said: "It was Di ... Seriously. Top right-hand corner. It's the photo with her hands clasped. I kid you not. It's absolutely spot-on. It's just there."
Their accounts seemed to tally roughly: in the top right-hand corner of the portrait of Charles I by Edward Bower on the wall at the end of the palace's lower corridor where they had been signing the books there hovered a famous image of Diana, once on the cover of Vogue.
Some said they had drawn close to the painting. But when they had done so, the image vanished. Mr Bennett continued: "A shiver went right down my spine."
Another man gibbered: "It's really thrown me a loop, that. Off the record, I think she's laughing at the Royal Family."
Leanne Buckerfield, a 56-year-old housewife from Staines who had queued for 10 hours, said: "Yes, we saw it. As clear as day. You know the pose, the one with her head cupped in her hands. She's got the tiara on as well."
Adrian Cooper, a 23-year-old office supervisor from Brixton, did not look the type to be easily taken in.
He gathered his composure. After a 10-hour wait, the apparition was almost too much. "It gives you a scare," he said. "Initially it just looks like a white mass. I didn't see it initially. Someone said: 'Did you see it?' She told me exactly where to look. It was that photograph where she had her hands on her face."
An hour later The Independent asked a second group of people to take a look at the painting of Charles I before leaving the room. No clues were given as to what they might be looking for.
One woman emerged in floods of tears. "I think she was looking over his left shoulder. I think she's got a red dress on. It made me jump. It suddenly hit me. It looked like Diana's face when she was younger, with her hair short. She didn't have anything round her neck. It looked very clear to me." When asked for her name, she refused. "You think I'm a crank," she said, sobbing.Reuse content