Doctor Who Season 10: 7 Big Questions After 'Extremis'

The intersection of the two stories, set in different time periods, suggests that the Doctor’s e-mail to himself might not be the only thing to have slipped through to his ‘real world’. Information could have been leaked out long before the Doctor sent his SOS.

When after saving Missy, the Doctor suggests that he be scanned to see how many times he has died, it throws up a surprising number. The death seekers know that he and Missy are Time Lords so it’s not his ability to regenerate that is brought to their attention. Perhaps it’s a reference to his recurrent fate in the confession dial (Heaven Sent), but it could equally be down to the fact that as a resident of Earth, in his different simulated versions, unlike Missy the Doctor has died multiple times.

We’ve no idea how many other simulations the Monks have run before the one in which the Doctor finally communicates the secret of the Veritas to his real world equivalent. All we know is that this simulation is the last, because the Monks view the trial as a success. The Monk who confronts the simulant Doctor claims to have killed him several times and somehow this information has already leaked out of the simulation. Maybe it wasn't 2,000 years but 2,000 simulants before the Doctor finally got to read the Veritas.

There is also the tantalising possibility that the real world has been communicating with the simulated world too, through River Song’s diary. Not only does the simulant Doctor quote from the diary at different points in the episode, he also quite unexpectedly has it in his possession. Is it a simulated version or the very same object somehow breaking into the game? Either way it is River's diary and not the Veritas that changes the outcome.