Who said what to whom?

The current gefuff about the Chilcot inquiry into the run-up to the Iraq war, which has been stalled for some time (years actually) over the extent to which the report can or cannot include correspondence between Tony Blair and George W Bush, seems to me and my (admittedly rusty) legal knowledge, rather straightforward and I find it difficult to understand why it has caused such a delay.  So, if I write a letter and send it to you, you own the letter (the physical piece of paper).  You can do with it what you will - destroy it, give it away, sell it, whatever.  The contents of the letter (what it says) on the other hand, belong to me, and you cannot publish that without my agreement. So what GWB wrote to TB can only be published with GWB's agreement, and equally what TB wrote to GWB can only be published with TB's agreement.  Simple enough?  Mind you, the question of whether they are willing to agree to publication is an entirely different matter, but as TB has said he is anxious for the report to be published, he presumably will not wish to hold it up by denying access to what he said??