A man I loved said his goodbyes and drove out of the story. His closest friend couldn't bear to see him off. The man got a final chance to say goodbye, a moment to say what needed to be said. One final handshake, one final hug, and a torrent of tears. And then, he was gone.
Some weeks later, there was a stranger in his place. Wearing the same clothes, and doing the same job. Sleeping in his room, eating at his table, and playing with his dog.
You know how this reads. It sounds like a regeneration story. The same long farewells, the same tear-filled moments, and the arrival of a new man, in the same job, but not the same face. It's not the Doctor, it's the Vicar.

And then there was one…
Tom Brittney left Grantchester in Episode 2 of Season 9, and I cried harder at television than I had since the end of Ted Lasso Season 3. I want to be clear: this is the height of irony here. A fictional Anglican Priest packed a fictional car and took a fictional job in Newcastle, and I had to pause the episode.
This transition, the changing of the guards, started a thought rolling in my head. Regeneration is a Doctor Who word, and were you to ask most people, the first connection they would make would be Doctor Who. Regeneration is actually a word on loan from, fittingly, the Bible, Titus 3:5 to be exact "-he saved us, by the washing of regeneration, and renewing." This renewal of the body by the grace of good ole J.C. and Co. The old man is "drowned," and a new one walks out of the water, a new man, but in this case literally. Doctor Who's central conceit had been playing out in a Church of England Parish, and the same vocabulary was in the priest's book the whole time.
So, with the preamble out of the way, let's do this properly. Eleven Series, three vicars, and one detective all in a show that finally found the third answer to the oldest problem in serialized television: what do you do when the man on the poster wants to leave?
Three ways to skin a ca(s)t

This never would have happened to the other fella.
The Bond Method - Denial
Sean Connery begets George Lazenby inexplicably begets Connery again begets Roger Moore begets an alternate universe Connery a third time begets Timothy Dalton begets Pierce Brosnan, begets Daniel Craig… and aside from Lazenby's fourth wall break, the movies don't even point it out. They have the same name, the same job, the same car, the same gun. And yet, they're each an entirely different human being. The audience is expected to engage in cognitive dissonance. Bond isn't a man, but a costume to be worn. A lot of people consider the Doctor to be a costume, but the method here is a different kettle of fish.

Believe it or not, these two guys played by the same guy are not in fact the same guy, but also the same guy simultaneously… its all a bit Wibbly Wobbly…
The Doctor Who Method - Mythology
Change the actor, but build the fiction around it. A body that renews itself, a reshuffled personality, and what started as a budget-fix becomes cosmology. It is honestly the best idea the series ever came up with. Every time, the new 'man' plays against type… with themselves. Peter Capaldi is the polar opposite of Matt Smith, and they know it. The contrast, the tension, and the conflict all come together to serve the passing of the torch.

Tonal whiplsh if you’re a binge-viewer…
The Grantchester Method - Door Number 3
Grantchester does what the other two couldn't; it fully acknowledges the change on screen, and it doesn't need complex mythology to explain it away. The Church of England already HAS a recasting protocol. It isn't "regeneration" per se, and it's called a Parish Appointment. Sidney Chambers, as you might remember from my last Grantchester article, leaves at the start of Season 4 to join the American civil rights movement. Will Davenport leaves in series nine with his family to take up a position in Newcastle. Nobody explodes into golden light, and nobody feigns ignorance of a new face. It may be strange to my Midwestern Lutheran Sensibilities, but Vicars get reassigned all the time.
So, that's where the comparison should come tumbling down like a house of cards. This is a cast change, the most ordinary thing in television. Shows like ER did it for years, except it doesn't feel like an ordinary cast change. It feels exactly like a regeneration, and I want to argue that's because Grantchester is using regeneration's grammar even though it isn't using its fiction.
The Grammar of Regeneration
Every time Grantchester does a handover, they hit every beat you'll find in a regeneration story, just with fewer bowties and more dog collars.
There is always a transitional episode, which allows for an overlap and contiguous storylines. Doctor Who has had these transitional episodes since Troughton came in for the first (televised) regeneration, but Bond couldn't care any less. These episodes provide both the characters and audiences with a chance to say their goodbyes. I discussed my hangups when it comes to the Chambers to Davenport handoff. I can tell you in all honesty that the second time around was done with far more care.
There is a standing set, as well. Where several Bonds may share an MI6, and the Doctor is rarely wholly without the TARDIS, Grantchester is full of constants. Mrs. C, exclaiming, "What the Dickens?" Leonard with Empathy on his sleeve. The last part is the resistance, the friction between the old and the new, the one who has to decide if they will accept the new man. Doctor Who has its Companions; Grantchester has Geordie Keating.
The Triune Cop, and the Perennial Parish

You see, in this analogy, Geordie is the Tardis AND a companion at the same time!
Robson Green is the only constant across all eleven series, which makes him simultaneously M, Moneypenny, and the companion who has to decide whether this new man is their Doctor. Masterpiece more or less maps out the arc for us: Sidney was a peer and a mate, Will was more like a Son, and Alphy is colder and more cerebral, whom Geordie is made to meet on different ground.
Three relationships, one man, and every time he struggles. Geordie's grief is the equivalent of Clara struggling to accept Capaldi. He doesn't want a new vicar; he wants his vicar. His initial rudeness (which is turned on its head somewhat with Alphy) eventually cracks by their second episode.
Another integral piece of note is the title of the show. The show isn't Sidney Chambers, or The Vicar and the Detective. The show is named for the parish, the real continuing character. The men who serve there come and go, much like the lifetime of a Time Lord.
Trinity of Themes
/im
Every time a new Doctor comes round, the tone of the show changes and adapts to suit the new one with the title. Eccleston's low-budget Sci-Fi Camp is replaced with the action and bombast of David Tennant. The Tennant Tenure becomes a Fairy Tale about a Madman in a Box. The Colder Capaldi becomes the brilliance of inventor Jodie Whittaker. And then Disney's cash leads to tears… and I don't just mean Ncuti Gatwa. The same sentiment carries through the transitions on Grantchester, each Vicar setting the tone of their time in the parish.
Sidney Chambers is living in a postwar melancholy, filled with Jazz, painful memories from the war he daren't divulge, and a crack in his faith that he fills with whisky. He's physically in the 1950s, but his mind and his soul still feel it's 1945.

Well technically the motorcycle went off into the sunset much earlier…
Will comes in like a lion, riding his motorcycle and wearing his armor of leather. No one in the village knew what to expect. His rock and roll aesthetic ushers in the rock and roll attitudes of the late 50's. He's fighting for social justice, and he's got a bone to pick with authority.
Alphy Kotteram arrives so suddenly that someone calls the police on him… in his own vicarage. Nair pushed for it because this is still the 1950s, and while a modern audience might not bat an eye, he knows that a brown man taking over an English Parish would not exactly the smoothest transition to make. Even Mrs. C has her own prejudices to confront, especially since she's the one who informed Geordie of a "swarthy" gentleman "breaking into" the vicarage.

A potentially brilliant run, brought to a close by the realities of showbusiness…
Doctor Who pushed those same boundaries with both Whittaker and Gatwa, and the Bond discourse on who should take the role has been arguing about Idris Elba for over a decade. Personally, I'd love Idris Elba as Bond; his demeanour fits amazingly well, and I could see him as a smooth spy. These are all very "Englishness-coded" offices. Bond is a spy, which is English state power. The Doctor is English eccentricity personified, with a dash of moral authority. The vicar is the English parish incarnate. The recasting process is never just about recasting, but a proposition of who gets to hold an English institution.
Grantchester's advantage is that it can easily put the answer into the script, while Doctor Who is stuck with press junkets and social media. The Bond Speculation cycle is still ongoing for the next replacement. Grantchester handled the transition in s9e3 by having Geordie confront an "intruder."
A Breaking of Comparisons
I've spent a lot of time making a comparison between these properties, but I've been glossing over the one thing Grantchester doesn't offer. So, let me be honest with you: the Vicars don't accumulate in the way Bond and the Doctor do.
Each performance from the other two deposits into a singular figure. Craig is making commentary on Moore. Gatwa inherits some qualities from Tennant. The roles get deeper because they walk where others have trod, and the role is somewhat "haunted" by every other person who's held the part. Alphy doesn't inherit memories or trauma, continuity or debt. (Though the Church does have a substantial bill for repairs…) The house is an inheritance, and so is Mrs. C, though he is reticent to accept a housekeeper. When Geordie looks at him, he's not seeing Sidney or Will, as much as he'd love to see them. He sees a stranger who lives in his friend's house and has taken his friend's job. The person doesn't carry over, but the position does.

It’s like Ncuti’s departure caused them to panic and choose the worst cliffhanger they could have used.
Doctor Who had to invent an alien biology to keep the role alive after their leading man left. Bond claims amnesia, except when it wants to reference the series itself. Grantchester came prepackaged with a solution from the 16th century, and it is the furthest thing from a gimmick. The Church of England has been regenerating its leads for over 500 years, but they call it succession.
Eleven Series, three vicars, and a somewhat grumpy detective, standing in the same churchyard, deciding to let yet another stranger in.