Vivian Maier was one of life’s eccentrics. A nanny who fell a bit short of Mary Poppins’ standards, she kept herself to herself, revealing little of her past or her passions to those who knew her. She might well have remained an unknown forever if it wasn’t for historian John Maloof. Sometimes things are just meant to happen I suppose.

Back in 2007, Maloof was looking for some photos of Chicago and picked up a box of old negatives at a storage auction. He knew straight away he had found something special, but could find out nothing about the photographer apart from her name: Vivian Maier. Maloof became fascinated with the work he’d discovered, and once he realised he was onto something, set about buying up all the other boxes of her property that had been sold at the same auction, eventually tracking down a storage unit where the rest of her possessions were still piled up. Maier had hoarded everything, her belongings auctioned when she could no longer pay the storage fees. Eventually Maloof amassed over 150,000 negatives, which he carefully scanned and examined. He found himself with a collection of stunning images, many taken on the streets of Chicago, dating from the 1950s onwards.

Maloof couldn’t find out much about the elusive photographer, but chanced on her obituary in 2009. It contained a few leads, enough for him to track down Maier’s old charges (most of them remember her as harsh, to put it mildly), her old employers (who didn’t seem to question how well she cared for their children as long as they were out of their sight) and eventually a few more personal acquaintances. But it’s clear from the interviews that even the people who knew Maier didn’t really know her; her main interactions with the world were through the lens of her Rolliflex camera. And though some of her photographs are clearly taken secretly, all sorts of people were willing to stop for a moment, stare back down her lens and let her capture a moment in their lives. What she said to persuade them we’ll never know.

We’ll also never really know why Maier kept her photography so secret. It seems like she knew she had a talent, but she lacked the drive, or maybe the confidence to have them more widely seen. Hundreds of them were never even developed – it seems that it was the taking of the photographs that was significant for her.  The rolls of film and endless strips of negatives were boxed up with everything else she owned, moved from house to house as she took nannying work to pay the bills. Maybe it never occurred to her that she didn’t need to.

While there’s clearly lots more that we’ll never know – and some debate about details that have been omitted from Maloof and Siskel’s film (worth catching the BBC Imagine documentary if you’re interested in finding out more, it’s a much better film) – this is nonetheless a fascinating profile of a talented artist who seemed overwhelmed by life. I like to think Maier would be delighted by her posthumous success, but I suspect she’d be appalled. What matters is the work she left behind, a stunning collection of images that are more than worthy of the comparisons that have been made to some of America’s great photographers: marketing man’s dream that I am, I immediately bought the book.