Fifteen years ago this week, BBC Panorama broadcast footage from inside Winterbourne View - a private hospital near Bristol owned by Castlebeck Care.

The programme showed staff pinning down, slapping, taunting and soaking residents with learning disabilities and autism. Eleven staff were later convicted, six were jailed, and the hospital was closed.

As Bristolians, we felt a particular shame that it happened in our hometown, the birthplace of Photosymbols.

When the defendants were sentenced at Bristol Crown Court, we stood outside on Corn Street with Bristol & District People First, holding placards and crying "shame on you" as they scurried in hiding their faces. People First members held signs made with Photosymbols images: "Waiting for Justice", "Inspection - Time to Get it Right", and "We Want Care - Not a Kicking".

Demo in a Box

That protest sparked something. We created 'Demo in a Box' - a pack containing a megaphone, blank placards, poles and notes on how to stage a demonstration. We sent them out free of charge to self-advocacy groups who requested one. We're still waiting for one to be returned.

Those same megaphones appear throughout the Photosymbols library today, in the images of self-advocates speaking up, demanding to be heard. I still see them in use.

The hardest shoot we ever did

Recreating the scenes from Winterbourne View in the studio was one of the most difficult things we've ever done. We worked with Bristol & District People First to act out the ideas. For the roles of the abusive staff we brought in two actors who understood the horrors of what had happened and wanted to contribute something to the work. That had to be handled with enormous care.

It was traumatic for everybody involved. Wayne Rogers sitting astride a chair placed over a resident. The restraint. The cruelty. The images we made that day are hard to look at, even now. But we had to make them, so that people could talk about what had happened, and about what was still happening elsewhere.

Those photographs are still being used, fifteen years on. It's a shame and a scandal that they need to be. They've helped people make sense of Winterbourne View, and of places like Whorlton Hall since.

What they do show is the power of an image to help someone process something almost too awful to put into words.

We hope we never have to take photographs like those again. In truth we know we will. So we'll keep doing what we've always done - supporting groups to speak up and be heard - in the studio and on the street.