One controller, only, who insists that "when ready leave control area on descent" is a mandatory readback. It's not a level assignment therefore it is my interpretation that it is not a readback requirement.
I believe that I am the controller referred to in the above instance and must disagree with Capt Claret and friends.
AIP actually states that a "level instruction" not "level assignment" as quoted shall be readback. Clearing an aircraft to "leave control area descending" is an instruction which refers to a level change and should therefore be readback.
I have spoken to numerous controllers with lots of experience (I have 15yrs) and they all agree that it is a clearance that changes a level and should therefore be readback. I find it interesting that the regional airlines have been descending OCTA for years and we have never had this problem and now all of a sudden the big boys start flying OCTA and it becomes an issue.
I am aware that some of us ATCs can get slack in regard to getting this readback but I personally will continue to ask for a readback and keep going til I get it... until proven otherwise.