Dear John (Short Trips: The Centenarian)

Prose One of a tiny group of stories from the "With Gemma and Samson" which the Eight Doctor promptly forgot about, which is something he's often prone to do. This brief glimpse of what a functioning story for this TARDIS team looks like suggests something akin to This Life featuring a grown up John and Gillian. It's also potentially a direct sequel to the prologue of this anthology, explaining what an entity which left Teddy Grainger's small body was and why, if I'd read the stories in between, there was something a bit off about him, the subsequent stories developing the aftermath.  This is a rich read with allusions to AA Milne and Poltergeist and neatly deals with the three in the TARDIS problem by having one of them getting absolutely blathered.
Placement:  The TARDIS Datacore suggests this might be post "With Mary".  Why not?