Doctor Who: EXACTLY Where Jo Martin's Doctor Fits Into Doctor Who Canon

Regeneration is one of the great inventions of the series, allowing it to continue long after the ailing health of it's first lead left the original show-runners looking for a way to continue without their main character. Over the years different episodes of the show, and the wonderful Terrence Dicks novels of the 70s and 80s, fleshed out regeneration so that we know its history and capabilities a little more.

The Time Lords used their power to catalogue history across the universe, bearing witness to all that was important in the rise and fall of countless civilisations. Regeneration was one of the abilities that allowed them to fit into these societies, literally changing their species that they might observe from the inside. This was actually shown on screen at one point when the Time Lady (it was a different time) Romana changed between several forms before settling on a more human form for herself while consciously regenerating.

Regeneration energy itself is not native to all Gallifreyans, instead being bestowed by the High Council upon those who become Time Lords. Each can have a total of twelve regeneration events, although it's long been known that a new regeneration cycle of twelve more may be bestowed upon Time Lords who have proven themselves worthy to the High Council. While intended for exploration purposes, renegade Time Lords like the Doctor tend to take inspiration from video games, using regeneration energy as extra lives when they get seriously injured rather than as a disguise to fit in.

It's obvious that this new Doctor is a previous regeneration of our Doctor, but where does she fit into the story?