I am in the process of painting my timber frame windows and when cleaning and sanding down I have noticed that there is a small gap between the window pane and timber frame on the interior (the stuff which was in the gap has come away etc. when prepping). I am wondering what I can use to fill the gap and then paint over it to give it a nice finish (the gap looks pretty ugly!).
Here's a picture of the gap.
I'm aware of window putty and decorators caulk but do not want to use the wrong thing and create more work for myself! Based in the UK if that helps with product recommendations.