Let's be honest, it is rarely a good idea for Doctor Who to actually integrate time travel into the narrative past explaining how they got to where the story begins.
But this story is ridiculously fun. Bonnie Langford carries it quite brilliantly and not enough can be said about how well Big Finish has turned one of the most disliked TARDIS teams into one you truly look forward to.
It's a loopy time travel, butterfy effect, Catch-22 story, and I grinned from beginning to end.