“Any other star,” says Guido Harari, “would have gone crazy. They’d have probably thrown me out.” It was 1am one night in 1989 and the Italian had been photographing Kate Bush non-stop for 15 hours. “We hadn’t eaten. We weren’t really talking. Just shoot, costume change, more makeup, shoot, costume change, more makeup, shoot.” You worked in silence? “Yes. It was like we had telepathic communication.”

Bush had asked Harari to do the official photo shoot for her new album The Sensual World. And then, in the early hours, Harari had a bright idea. “I thought she looked like the figurehead of a ship. So I would make her look as though she was swimming towards the camera underwater.”

Harari decided to create this image by shooting Bush in a Romeo Gigli dress in front of a rented painted backdrop that looked like a Pollock painting. Then he would ask her to step out of the shot, rewind the film on his Hasselblad camera and shoot the backdrop again, making it look like she was a swimming through a submarine world of drips and blobs.

And then he had another idea. Why not have two images of Kate Bush on the same frame? “And then I thought: why only two Kates? Why not three Kates – all swimming in the water? She had to stand really still so she wouldn’t go out of focus because I was using a wide aperture, so there was no depth of field. She had to walk out of the shot, then back in, stand very still, and do the same again. I knew it was going to be great but it was going to take time and patience – and you don’t get either often from famous people when you’re photographing them.”

Isn’t that when her PR minder should have intervened and said: Guido, enough already? “Well yes! But there was no minder. She was never part of what she called the machine.” As we chat, Harari shows me shots from his new book The Kate Inside, which documents his 10 years photographing the British pop star. It shows her wearing a T-shirt that says: I am a prima donna. “My God,” he says. “I’ve worked with some real prima donnas, not to mention any names. She wasn’t one of them.” Indeed, there is a copy of her handwritten thank you note which says: “You’ve made me look great.”

Harari has made his name over the years with disarmingly odd images of musicians. Leonard Cohen asleep on a little table before a huge painting; Tom Waits strutting in an improbably voluminous cape; Laurie Anderson and Lou Reed in a moment of tenderness, her nuzzling nose disappearing into his open shirt. Harari was a Kate Bush fan from the first time he heard her first single, Wuthering Heights, on the radio in 1978. “She was a pioneer, especially in Britain where no solo female artist had had a number one-selling album until she came along. And you had the sense that, despite her wistful manner, she had balls of steel.”

The photographer first met her in 1982 in Milan, when she was promoting her album The Dreaming. In the book he describes his first impressions:“Beautiful golden eyes, pouty lips, a big mane of hennaed hair.” Bush and her dancers had just come from a TV studio. “She was wearing what looked like decaying astronaut gear,” he recalls. “I had my equipment with me, so I asked them to improvise. What amazed me was how she switched. She seemed to be this shy girl then suddenly this wild beast came out. ”

In Milan, Harari showed her proofs for a new book he was making aboutLindsay Kemp. The choreographer had trained the teenage Kate Bush in the mid-1970s, becoming a mentor to her, as he had been for David Bowie. “So my book was like a calling card – showing her that I understood where she was coming from artistically.”

Three years later, Bush called, asking if he would do the official shoot for her album Hounds of Love. “I went to meet her at her parents’ farmhouse in Kent. She had built a 48-track studio. One thing that really struck me was that there was no glass between the control room and where the musicians recorded. It was a place of silence and retreat from the rock’n’roll world. She had no desire to go to parties or be famous. Instead, she had her family around her. Her father was her manager and her brother had taken photos for her previous albums.”

For the Hounds of Love shoot, Bush told Harari that she would bring clothes that would be brown, blue and gold. “Nothing else! No other clues! So I got some backdrops I thought would go with those colours, and at 8am she turned up at the studio with her makeup woman and a few outfits and we went to work.”

Most of the photographs in Harari’s book have never been seen before. “There are lots of outtakes. What would happen is, at the end of the day, I’d have hundreds of rolls of film which I’d edit and then send to Kate. She’d send, say, four images to the record company. What nobody has seen until now is the progress through the day’s shoot. They really give a sense of her. The way she’s goofy one minute and then posing the next.”

After doing the photography for Hounds of Love and The Sensual World, in 1993 Harari was asked to be the stills photographer for her 50-minute film The Line, The Cross and the Curve starring Miranda Richardson, Lindsay Kemp and Bush, and showcasing songs from Bush’s album The Red Shoes. “It was a great invitation because I could be a fly on the wall. No fancy set ups, just me recording what was happening.” He’s particularly proud of his shot of Bush asleep on set in her curlers with Kemp posing behind her head. “I know she was disappointed in the film, she maybe thought it was a flop - not commercially but for her. So the photos were never published.”

That shoot marked the end of their collaboration, but there could have been another chapter. In 1998, Bush phoned Harari and asked if he would photograph her with guitarist Danny McIntosh and their newborn son, Bertie. “I said, ‘No. This is a private moment, keep it as it is.’”

Harari goes back to that Hounds of Love shoot, recalling Bush’s rapid transformations. First she appeared in an orange jacket with padded shoulders. “She looked like Joan Collins. And then she went off to the dressing room and came out wearing this fabulous purple scarf, like a woman from 1900. And then she disappeared again and I wondered where she was, so I went to the dressing room. And there she was sitting in a chair in this thick white Kabuki make up. She looked great, even with the powder still on her shoulders, but there was one detail missing – so I took her lipstick and smeared it across her lips.”

• The Kate Inside is available from Wall of Sound Gallery. An exhibition of 50 photos from the book runs at Art Bermondsey Project Space, London, from 13-30 September