I have to admit, I think if the person asking is the subject of your photograph, it's completely reasonable of them to request the image for free. Doesn't kill a photographer to be generous with the subject of their images.

But if it's nothing to do with the person asking, I'd say not. Today, I sourced pics for an article with a magazine. Thought I could ask a friend for a shot I'm missing, but then thought 'no - he sells on Alamy' so I found his shot on Alamy and sent the magazine the link to it instead. That's the right thing to do.

But when a guy photographed me in the street a few years ago, expected me to model in my steampunk gear - pose in a variety of different ways - and then refused to send me a high res shot with permission to use it, well, he wanted me to model for him - I assumed he'd let me have a shot, or take one with my own camera that I could take home. A favour for a favour.

Except it was all one way. Now anyone else who asks me to do that will get a less cooperative response.