My interpretation is that the global history is a CF thing. A local history is not prohibited, it is just a different thing and is not described by the CF conventions. I don't want to put the Iris history in the global_attributes as it is almost always going to be cube specific and separating it enables the CF global history to be better preserved (i.e. we don't mess with it), solving some of our users issues. It also sidesteps the issue that the Iris history timestamp is not in teh expected format for the global CF history attribute. Of course, cube.attributes['history'] will give you the local one if both are present. If we go down this route, I propose we identify special behaviour beyond the generic local beats global in subsequent PRs.