So I sat there on my little plastic stool, nursing a cup of tea, with my back turned to the easel. It went on for an hour or so. My wrist still hurting, and not one single painting inspiring me to pick up a brush.
I decided if I couldn't get on with anything, I should werk out how to do something new: this 'something new' would, at some point, warrant building a set of tall, thin canvases. I measured and scaled up the subject by 10 times - 170cm x 9cm.
Next I went to the dusty jigsaw workshop and set up the mitre saw. Conclusion: if I was to cut any lengths of timber to 9cm, I would definitely be risking my fingers. I did a test, and realised that the bloody thing doesn't even cut a straight angle anyway (this explains why I had to make a wedge to get the last canvas I made square.). Tried to adjust the blade, made it worse. Then concluded that even if it did cut straight, there is absolutely no way of making a precision cut, as there are no guides on the bed to show where the chop will be made.
Much swearing followed... then I went and bought one of these old-fashioned manual bits of kit on eBay for a fraction of what the electric one cost. It's built like a tank and painted in green hammerite, just what the doctor ordered.