Ben Miller's Doctor Who diary

“Darling, can you ride a horse?” I’m on stage at the Vaudeville Theatre in London, doing my warm-up, which basically consists of eating cake while chugging a triple espresso. In a few minutes, the curtain will go up on The Duck House, a slapstick-farce about the expenses scandal. Six months in the part have left me with a cavalier attitude to the truth. “Who wants to know?” I ask, “Doctor Who,” says my agent. “I’m a natural,” I say.

10.19PM

Seventy-three sight gags later, I return to my dressing room to find an unusually verbose email from my agent. “B – Interest in you as Sheriff x.” The attachment reads, “Robot of Sherwood by Mark Gatiss.” Is this a wind-up? Is it really possible I could be in an episode of Doctor Who? Wide-eyed, stripey scarf-wrangling Tom Baker was my first idol, and the show gave me a fascination with time travel that inspired me to study physics. I lock my dressing-room door and sit down to read...

Like joining MI5

14 March

Everything about Doctor Who, I’m beginning to learn, is shrouded in secrecy. Landing a part is like trying to join MI5, only with tighter security. My overwhelming love for the script has been relayed through the official channels, and since then... Nothing. I decide to say nothing to my boys just in case it doesn’t work out. Both of them have been schooled in all things Time Lord since birth. Sonny, eight, has an enviable collection of sonic screwdrivers and Harrison, two, genuinely believes he is a Dalek. Pull this one off and I may be their hero for ever.

Ben Miller as the Sheriff of Nottingham in Doctor Who

A secret chat

16 March

Paul Murphy, the director, calls me for a chat. We have an in-depth discussion about my character and the way he intends to shoot the fight scenes. It’s all very professional, but what I really want to ask is, “Will the Master be coming back?”

My bag is packed

7 April

It’s on. Shout it from the rooftops: tomorrow I have my first day’s filming on Doctor Who. The last few days have been a blur of costume fittings and make-up tests. Claire Pritchard-Jones has fashioned me an extraordinarily malicious suite of facial hairs, and Howard Burden has kitted me out in so much tasselled leather I wouldn’t look out of place playing bass in Nine Inch Nails. My bag is packed, and on the train to Cardiff. Which is a shame, because I just got off at Newport. Basically I saw a castle and panicked. I forgot that every Welsh city has a castle, just like every English one has an IKEA.

My kingdom for a horse rider

8 April

First day of shooting. I’m about to do some marauding. Somehow, from nowhere, an entire medieval village has been created in the Vale of Glamorgan. I can’t believe the budget. On a two-acre plot are at least a dozen wattle houses, kitted out with authentic cooking implements, with suitably ancient breeds of chicken pecking in the dust.

I sidle up to one of the crew. Amazing attention to detail, eh? He looks at me strangely. “It’s Cosmeston Medieval Village, Ben. It’s a theme park.” I nod sagely.

“Do you want to meet your horse?” I am led towards a sable-black beast 15 hands high that looks like the steed of a Norse warrior god. Perched on top of it is the bass player from Nine Inch Nails. Oh – hang on, I’ve got a double. And he can ride! This just gets better and better.

Back at base, I bump into Peter Capaldi, who is filming a different episode. He greets me warmly, which is a relief, as the last time I saw him he tried to throttle me with a yard of piano wire. He claims it was part of the play we were doing at the time, The Ladykillers, but I have my doubts. He is dressed as the Doctor, and something about the frock coat and the tieless, buttoned-up white shirt is instantly iconic. Suddenly I place it; that’s how Peter always dresses.

So, how is he finding it? “I’m like a kid in a sweet shop,” he says, grinning. “I was meant to have a day off yesterday, but I saw they were shooting a fight with the Daleks, so I came in anyway. Couldn’t miss that, could I?”

Tom Riley's Robin Hood with Peter Capaldi and Jenna Coleman

I wield my sword

9 April

Swordfight rehearsal. A little humbling. Tom Riley from Da Vinci’s Demons is playing Robin Hood, and as well as being a devastatingly handsome, impossibly witty and brilliant actor, he is a master of the blade. When I wield my sword I look more like a painter and decorator trying to get some wallpaper up in a hurry.

After five minutes’ swashbuckling I am exhausted and call for time out. Tom offers me a carrot stick. I take one, artfully draping my coat over my bag of doughnuts.

Kid in a candy store

17 April

Possibly one of the most exciting days of my life. We arrived early at Caerphilly Castle to see hordes of extras thronging the gates. I check the call sheet, which lists the day’s business. No sign of a crowd scene.

Have they changed the shooting order? My friend on the crew shakes his head. “Those aren’t extras. Those are the fans.” I have Sonny with me today, and his eyes are out on stalks. One of the true joys of the set is how welcoming it is to children. Whatever’s happening in front of the camera, you can guarantee that somewhere behind it is a huddle of lucky ten-year-olds wearing head- phones, listening in to the scene, their eyes glued to the monitor.

At the end of the day, Peter and Jenna sign a Day of the Doctor poster for Sonny. Peter signs his name over the picture of Matt Smith, and Sonny and I smile appreciatively. This is the only show in the world where that makes complete logical sense.

Final cut

1 May

Last day of shooting. The studios here in Cardiff rival anything I’ve seen in the US, and we have spent the week shooting on colossal interiors with an army of crew.

My last-scene-but-one is my swordfight with Tom Riley. What I hadn’t quite counted on was the fact that we rehearsed with wooden swords, but the ones we are shooting with today are very, very metal. After some particularly inept clanging on my part I end up making a new joint in Tom Riley’s thumb. He is far too polite to say anything, but when we say our goodbyes I can’t help noticing he shakes my hand with his elbow.

For my final scene I am to be winched right into the roof of the studio on a wire, then dropped some three storeys onto a crash mat. Paul Murphy is shooting in a different studio, and directs over the intercom. As I dangle in the rafters, waiting for the first assistant to call it, I can’t help feeling that this is a metaphor for the whole job. I’ve been carried to great heights by this magnificent team, and had experiences that will last me a lifetime. And now I’m about to be dropped back into reality.

“Action!” says the first, and I kick and flail into the abyss, the wire pulling tight inches above the mat. Everyone applauds. Tears well in my eyes. Then Paul comes over the radio, “Can he do it again? The monitor cut out and I missed that one.”

Doctor Who is on BBC One tonight at 7.30pm