A classroom teacher is employed to prepare and teach, so they are responsible for writing their lesson plans. Yes, the HOD produces the long term plan and the idea of sharing it out amongst staff means that everyone shares the load. However, I often find that the quality produced is widely variable using this approach. I've tended to circulate the plans I've written as I know they are in the detail I would expect from others and I mark them as 'suggested'. They can then adapt what I produce and share their ideas with the rest of the faculty so that there is a bank of material to draw upon and that my plans, ultimately, are not the only ones available.