I applied some fire cement to the collar of the stove, where the chimney meets the stove, where I could see some smoke leaking out, but that didn't solve the problem. The next step was to replace the fire rope, which is a gasket on the main door of the stove. It looked like it might have perished. We got some fire rope and I set to work on a very dirty task.
The first step was to take the door off the stove. That was easy enough, it comes off like a Jeep door.
Next, I had to remove the old fire rope. It had perished a bit and was really really crusty and compacted. I used a screwdriver to dig the old rope out of the channel in the door. It was pretty gross.
Next, I used white spirit (rubbing alcohol in the States?) to clean the channel of any leftover bits of rope, glue and creosote. The groove needs to be clean and dry before you can put in the new rope. I also tried to clean the glass a bit but I didn't get very far.
Finally, I put in the fresh rope. You lay a bead of glue all the way around the groove, and then push the rope into the groove, making sure the ends meet and there aren't any gaps.