Regeneration is an inevitable part of any Timelord's story, but that doesn't mean it's not tough for Doctor Who fans. The prospect of meeting Jodie Whittaker's Doctor in this year's Christmas Special, 'Twice Upon a Time', was incredibly exciting, but also tinged with sadness. After all, it meant bidding farewell to Peter Capaldi's Doctor after four years and some 40 episodes.

One young fan, nine-year-old David McGilloway from Ireland, was apparently "dreading" the regeneration, until he received a handwritten letter from Capaldi himself. The letter, which his father Brian shared on Twitter, is completely adorable and very reassuring.

"Dear David, I hope you are having a very merry Xmas," Capaldi writes. "Xmas is always good fun. Well, not always. Not every single second. Regenerating is not completely good fun. And it usually happens about Xmas-time. But you know what? Even though it can be a little bit icky (like really bad flu) it has always, always turned out good for Dr. Who.”

Capaldi continues: “The new doctor always becomes your favorite and the one that goes… well, he never really goes, he is always there, somewhere in time and space, and if you think about him hard enough you’ll see him, and he’ll see you. It’s like the Doctor says, ‘Everything ends and it’s always sad. But everything begins again, and that’s always happy. Be happy.’ So, have a brilliant Xmas, a happy new year, and a wonderful life — I’m sure you will. All the best, Peter Capaldi, Doctor ?”

https://twitter.com/BrianMcGilloway/status/945951773046595584

It's hard not to agree with Brian McGilloway when he calls Capaldi "such a kind man." Then again, the actor definitely would have understood how much a letter from the Doctor himself would mean to a young fan. Back in the early 1970s, when he was just a teenager, Capaldi was such a huge Doctor Who aficionado that he wrote to the BBC asking if he could run the fan club. He got a very courteous response from a corporation employee, but as he found out on The Graham Norton Show a few years ago, that same employee wasn't quite as polite behind closed doors. Watch Capaldi reliving the "total anorakness" of his Doctor Who fandom below.

Which is your favorite Doctor Who regeneration episode of all time?