You know the iconic Doctor Who story “The Tenth Planet,” that features the first regeneration ever on the hit BBC sci-fi series? Well, that wasn’t always how it went down.

An original draft of the 1966 script has reportedly surfaced, and it has quite a few differences from the version we all know and love. Author Michael Seely unearthed the script in the attic of late Who writer Kit Pedler while researching a new project.

William Hartnell passed the keys to the TARDIS on to Patrick Troughton in the fourth season serial, but the decision apparently came late enough in the process that the ending of the episode had to be completely reworked.

Seely released this intriguing pic as proof of the find:

The author went on to explain the context of the script, which was first written a month before Hartnell actually decided to leave the series. More than anything, it’s an interesting peek at some storylines that were originally in place before Hartnell’s exit took center stage. Here’s what Seely had to say about it, via SFX:

“The structure is more or less the same, though a lot of the dialogue is different. Some things were cut, especially involving the Cybermen. For example, the Cybermen planned to convert [companion] Polly and the Doctor into Cybermen towards the end of the story, and kept them prisoner in what they described as a waiting room. The most eye-catching difference is what didn’t happen at the end of the episode... Gerry Davis and [producer] Innes Lloyd were always very diplomatic and tactful in their interviews. Both died in 1991, long before ‘warts and all’ interviews became the norm. We know that William Hartnell was being persuaded to give up the role he loved over the summer of 1966, and that they were sounding out replacements. He only decided to leave in the middle of July, the month after this draft was written.”

Check out Hartnell’s regeneration below. Here’s hoping the full script eventually makes it out into the wild, so we can at least read what this scene replaced:

(Via SFX)