"I don’t actually know if I can speak... to be honest...’cause I’m... it’s just, so powerful, isn’t it?” Director Carol Morley’s stuttered words after the premier of her new film are met with silent agreement. “Just to be here, it feels quite... it’s very moving.“

As the credits roll, the audience turn to one another, struggling to put their first thoughts into words. We have just seen Dreams Of A Life, the moving, intriguing and disturbing story of Joyce Vincent, who died in her flat, aged 38.

Her body was discovered across the bustling high street from where we are gathered at Wood Green Cineworld in 2006 by bailiffs, knocking down the locked door of her bedsit to collect rent arrears. Past the mound of unopened post, past the dirty dishes waiting to be washed in the sink, amid a pile of unsent Christmas presents, they found her corpse. It had lain there, the television still on, for three years.

The gruesome story made the tabloids but details were notably absent.

“I was intrigued,“ explains Carol, who dedicated the five years since to telling Joyce’s story. “There was no photograph of Joyce and it was a very anonymous story. A very extreme story because of the three years, but it was the potent image of the television flickering over her decomposing body for all that time that captivated me as a filmmaker.

“I really felt do we just walk away from this? Do we just let this go?“

Carol, who came to prominence with her award-winning documentary The Alcohol Years, didn’t let Joyce go for a second. Tracking down those who knew her, Carol filmed interviews with ex-boyfriends, former colleagues and flat mates, to create a picture of a sociable, humorous and beautiful woman.

“She was just so far away from the tabloid stories.“ Carol discovered not a junkie or lonely outcast but a complex woman who “had always seemed successful, even as a child,“as one friend recalls, who was always “immaculately dressed“ with a “wicked sense of humour“.

In the film, scenes from Joyce’s life are reconstructed by actress Zawe Ashton.

While talking about the filming process, a crackle on the microphone derails the Fresh Meat actress’ train of thought. “Sorry. I’ve gone off piste,“ she utters. “I feel very emotional this evening.“ “Questions got thrown up every day doing this,“ explains Zawe. “I had to live moment to moment. I was so happy to bring her to life and not think about Joyce’s end.“

The dramatisations paint Joyce as a chameleon-like figure who had endured a difficult childhood and had aspirations to be a singer. A life that chimed with Carol’s own.

“I did, no doubt, become obsessed with Joyce,“ reveals Carol. “I grew very close to her, even though I had never met her, and I felt that we had so many parallels in our lives, I could understand her to some extent.

“I found out we’d once lived on the same street in London. Joyce was the same age when her mother died as I had been when my dad died.“

After years of painstaking research and appeals for information, Joyce’s death remains something of a mystery.

“It depends what you’re seeking answers to,“ explains Carol. “If you’re seeking answers to how Joyce died, the inquest recorded an open verdict, so we will never know how, we will never know that. To all these questions – I’m baffled.

“For me, it was much more important to look at how she lived.“

Despite its subject matter, Dreams Of A Life is not a morbid film but one that looks with poignancy at the reality of modern living, and one that raises more questions than it answers.

“In an age of communication, we can be so dislocated and alone. You see a headline, you write someone off, you walk away. What this film says is never walk by, never walk away and never underestimate anyone. That’s what I found out making it. That’s my answer.“

The audience leave the cinema, pacing home in the freezing air along the same streets that Joyce too had walked just a few years ago. A man pushes through the crowds at the Tube station, jostling past strangers he might never see again.

Dreams Of A Life is in selected cinemas now. www.dreamsofalife.com