So it seems you can over knead by hand. Although I think the commonly held belief that you cannot perhaps doesnt include doughs which have been autolysed?
Yesterday I made Pain au Levain with Wholewheat flour from Hamelmans Bread. I autolysed for 45 mins but then kneaded for a further 10 minutes or so and quite vigourously-unsure how long or how hard as guidance in the book is for mixers. The dough did seem quite strong after this. As per instructions I then included two S&F's. Following all the other instructions the resulting bread was really tightly crumbed and took a long time to, only moderately, spring in the oven. It also took longer than expected to bake resulting in a lack of aroma and a dry course texture.
Today I followed exactly the same routine but after autolyse I kneaded much less vigourously for only 3 or 4 minutes at most. The resulting bread today sprung beautifully and baked in less time. It's fragrant and has a soft, pleasingly moist crumb.
I'm starting to realise on this great baking journey that developing gluten to the nth degree isnt the be all and end all. One kind of thinks it is necessary to develop gluten as much as possible in all breads when one first starts out.
A contributor here, shortly after I joined, suggested to me that flours around 11-12% protein were probably more suited to the sourdough breads I'm making than the 15% canadian flour I was using at the time. I didnt quite get that at the time but I'm starting to understand it now.
I think I need to be a little more moderate and a little more gentle!