Earlier this year, a man using an outdoor public urinal shouted obscenities at me as I walked past. When I refused to acknowledge him and started walking faster away from him, he chased me down the pavement, even though it was half-past eight on a weekday morning and the road was busy with people on their way to work. I shared what had happened and my sense of fear and outrage at it on Twitter, and the response was a revelation - so many women got in touch to relate similar incidents.

Whereas it would once have been taboo to make this kind of thing public, women choosing to speak out about it has become something of a trend of late. Last month, Liz Gorman, a photographer from Washington DC, wrote about how a man had casually sexually assaulted her on the street in broad daylight:

I was in Dupont Circle at 3:30 pm yesterday and was sexually assaulted while walking. In my hometown, in a nice neighborhood, in broad daylight, in public. I’m a city girl; I walk fast and have rules. A man pulled up behind me on his bicycle and reached up my skirt. He put his finger into my vagina through my underwear. He laughed and biked away. That was it. No 10-5, no catcall. No exchange. I didn’t see his face. At least when I was robbed at gunpoint, I knew who to look for on the street.

Gorman’s story went viral. Washington Post columnist Petula Dvorak implored women to keep the tide of similar stories coming, acknowledging that while “police are busy, and far more heartbreaking stuff happens every day”, making incidents public and reporting the assaults “might help”.

Every woman I’ve ever spoken to on this subject has her own story to tell. They vary from the frankly quite funny (“I kept ignoring him when he shouted at me so he actually laid his jacket down in a puddle in front of me in the manner of Sir Walter Raleigh to try and get me to speak to him”) to the terrifying-sounding one that Nat Guest has written about here.

But this is precisely the problem with this whole issue - so much of the evidence is anecdotal. This by no means belittles or doubts individual experiences, but it’s an unfortunate truth that a long string of individual tales is easier to brush off or ignore for those already inclined to do so. Even something like the Collective Action for Safe Spaces site, where victims can post accounts of their experiences, is just that – a string of anecdotes that can help to raise awareness but will struggle to muster the collective impact to do much more.

In Gorman’s case, there was a witness to her assault so that once she called the police there was some action they could take. But in many cases, even if the woman does choose to make the report to the police, there is very little they can do to apprehend the offender - the shocking, fleeting nature of these things mean that the woman may not have even glimpsed her assailant before they were gone. And what of cases that aren’t so easily defined as “assault”? In my own anecdote, the man made no physical contact with me, although he did expose himself, shout at me and pursue me down the road a way. What if there’s only lewd shouting? The woman is still made to feel uncomfortable, afraid, unsafe - and above all powerless.

A recent survey for Gallup confirms that this is very much a problem experienced by women, and that living in a first world country doesn’t necessarily make women feel any safer walking alone at night. The survey, conducted across 143 countries, also found that the gap in this feeling of safety is most pronounced in Europe, where 20 per cent more men than women said they would feel safe walking alone at night.

However, the debate about street harassment has just been ignited in Belgium by the release of some hard evidence of how bad the situation can be. Sofie Peeters, a final-year film student in Brussels, has made a documentary called “Femme de la Rue” and which might just have provided a way of moving the discussion on from the endless string of unverifiable anecdotes. It’s her use of a camera hidden in a pen to film the kind of harassment she routinely experiences that has enabled her film to really escalate the situation - as you can see from the trailer below, some of the footage is genuinely quite shocking, not least in its frequency and the way it melds with ordinary life:

I emailed Sofie for some more details about her own experiences, and what caused her to make the film in the first place, and she sent some explanation:

Mostly it stayed “innocent”; guys staring at you like you’re from outer space, guys clicking their tongues or making other noises, while passing they said something like “Hello baby, you want to come with me?”… This may not sound very disturbing, but it is. I don’t feel at ease, treated this way. It makes me feel like a cheap chick, who does not deserve respect and is on the street for the entertainment of men. I felt like public property. In my quarter it happens very frequently. One time, during the summertime, I walked from Brussels south station to my appartement in Anneessens, a walk of 15 minutes, and just for the fun of it, I counted the times I was approached like this. It was eleven times. It drives you crazy. But that was just the “innocent” part. I got chased down the streets, I got insulted and so on. Guys who don’t want to hear a “no, thank you” on questions like “Can I buy you a drink?”, “Can I have your phone number?”, “Do you want to have sex with me?”. They follow you around, even if you clearly state that you are not interested and wish to be left alone. If you get mad, they insult you: “Whore”, “Slut”, “Racist”. This is verbal, sexist harassment and I don’t accept it. I also heard of girls in my environment who were physically harassed as well, but I am glad to tell you that I had no experiences of that matter.

She adds:

“I don’t mind guys asking me for my phone number. I don’t mind flirting or making conversation with strangers. But this has to happen in a respectful way, not in an intimidating way.”

This is a really important point – she’s not suggesting that all interaction on the street should end or that men should never approach women – just that behaviour that is clearly unwelcome and inappropriate has to stop.

Her film, which was shown on television in Belgium last week, has provoked quite a row there. A lot of attention has focused on the fact that a lot of the men in Peeters’ film are immigrants to Belgium, mostly of African origin. But in various TV and newspaper interviews, she’s made pains to emphasise that she wasn’t targeting a particular community - Anneessens, the neighbourhood in central Brussels where she lived and where some of the film was shot, is a predominantly North African area, so it just reflected her own experience not that of the whole city or all women.

She told Flemish channel VRT:

“It was one of my biggest fears. How to tackle this subject without making the film racist? But this is the reality: when you're walking around Brussels, in 9 cases out of 10 these insults come from a foreigner. ”

However, Peeters’ film has done more than just start a debate. Joëlle Milquet, Belgian interior minister, said that she was struck by the film, and reaffirmed her intention to put a bill before Parliament in September that will legally define the concept of sexism and penalties for committing it – you could receive a ticket for €250. She said: “There is no doubt that sexism is intolerable and must be fought in the strongest terms.” The documentary has become such a high-profile topic in Belgium that pressure will be on politicians to make it work.

Whether Belgium’s new law can be enforced with any success will of course be the true test of the minister’s good intentions. Femme de la Rue is one film, about one woman's experience of one area of one city, so of course it has to be viewed firmly in that context. We know, though, that it is a problem for women all around the world. But what Peeters’ film has demonstrated is the power of hard evidence in a matter that has bubbled along under the surface, sustained only by anecdotes and given prominence only occasionally when stories like Gorman's capture the internet's attention. By taking her hidden camera out onto the streets, though, Sofie Peeters has provided unequivocal proof of her own experiences, and suddenly the behaviour they show is much more difficult to ignore.

Find out more about 'Femme de la Rue' including details of upcoming screenings at facebook.com/femmedelarue