Deep Who lore. After Classic Who was cancelled, all that came out of the franchise was the TV movie, novels, and unofficial audio dramas. Lungbarrow is the most famous of the novels, and was the last of the Virgin New Adventures range to feature the Seventh Doctor. It answered a lot of the questions that'd been subtly raised as part of the Cartmel Master Plan, going into detail on just who the Doctor is, while making him more mysterious and alien at the same time. Where in NuWho, the Doctor grew up in a barn, the VNAs had him "grow" up in a massive house full of living statues, where his tutor is Badger, a member of a mechanical race that's seven feet tall. Time Lords do not have parents, they are not born naturally. They are "born" inside machines called Looms, weaving a new Gallifreyan into existence from the base matter of reality.
Lungbarrow is more canon than the barn. It doesn't matter that one has been out of print for twenty plus years and is virtually impossible to get ahold of physically, it's down to the quality.