Russell T Davies has created new incarnations of the Doctor beyond Jodie Whittaker

Fair warning – if you read beyond this point we're heading into minor spoiler territory, especially if you want to experience all the book's surprises in-page.

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Still here? OK, let’s slow things down a bit to explain what we mean. As you may or may not remember, in the broadcast version of the episode, Rose (Billie Piper) goes to meet an obsessive fan of the Doctor called Clive (Mark Benton), who has uncovered pictures of Christopher Eccleston’s Ninth Doctor throughout history that convince him of the Time Lord’s immortality.

In Davies’s updated text, however, Clive’s pictures also include previous incarnations of the Doctor – mainly Tom Baker’s Fourth Doctor, appropriately – which makes perfect sense without undermining the simpler take the TV series presented. If the Third Doctor hung out in, say, World War Two, of course someone in 2005 could know about it – but equally, when reintroducing the series to the world it would have been over-the-top to dump ALL of Whoniversal history on viewers in the first 45 minutes.

And with the benefit of hindsight, Davies also fills in a few of the Ninth Doctor’s successors who would have been rattling around in pre-2005 history for true obsessives like Clive to uncover (time travel makes things very confusing), including Peter Capaldi's recently-departed Twelfth Doctor.

But it’s at this point that things get really interesting, because Davies doesn’t stop by including future Doctors that we’ve met (David Tennant’s Tenth Doctor also features – although Rose looks away before she sees any photographs of him).

No – he creates NEW incarnations of the Time Lord as well, who would presumably follow Jodie Whittaker’s Thirteenth Doctor, as you can read in the excerpt below (which also includes pretty clear references to the Eleventh and Twelfth Doctors).

We hope new showrunner Chris Chibnall has read this, because we can’t WAIT for the giant frog episode this autumn.

Of course it’s unlikely that the series will follow this exact prediction for any future Doctor Who actors – if nothing else, casting a child who wouldn’t age out of the role would be murder – but given the Doctor’s potentially infinite number of future selves, who’s to say they couldn’t be in there somewhere? And if they are, well, the Doctor only has him/herself to blame for being surprised by new bodies post-regeneration. Just do some research!

Anyway, in the end it’s a sweet little joke from Davies that seems to poke fun at some fans’ upset at Whittaker’s game-changing casting, as well as demonstrating something about the new Target novelisation project (which also includes adaptations by Steven Moffat, Jenny T Colgan and Paul Cornell) as a whole:

Thirteen years on, an old episode of Doctor Who can still be fresh, vital and exciting – and completely full of surprises.

The new Target novelisations of Rose, The Day of the Doctor, The Christmas Invasion and Twice Upon a Time will be released on Thursday 5th April