Who did the Doctor Trust the Most? There are two Doctors in this episode. A much older one and a much younger one. The younger Doctor tells River to her face that he doesn’t trust her and it’s Amy who wins his trust.
The older Doctor who we see at the beginning of the episode has his own diary matching River’s and is reminiscing with her about their adventures together. He is also the one to send the invitations to his death — which Moffat takes the time to point out are numbered in order of who he trusts most.
The person he trusts most in this world is obviously himself. And in a contrast to how the younger Doctor behaves, River receives the second envelope and Amy receives the third. While Amy remains The Doctor’s best friend, The Doctor we see at the beginning of the episode and who sends the invitations is the one who is about to marry River in the finale. Before he marries her, he’s grown to trust her completely which is a theme that had been building since Silence in the Library where she reveals he will trust her so completely that he will tell her his name.
We really don’t see much of The Doctor who marries River, but there are 200 years between the premiere and the finale where he breaks River out of Stormcage at night (as he has promised to do and as we see in the older Doctor who has a matching diary of adventures). But when he gets to the finale, he is thrust into a situation with a much younger River who he is quite obviously frustrated with.
We only again see his relationship with her on equal ground in 7x05 where we can see how much closer they had become. She is now out of Stormcage and he’s already spent those nights with her. Here, they act like a married couple - something we hadn’t seen as we never saw them at a linear point in their relationship.