John Finnemore is one of the best comedy writers in Britain. He writes every episode of the sitcom Cabin Pressure, which returns tonight for a fourth series with its all-star cast of Roger Allam, Stephanie Cole and, if you please, Benedict Cumberbatch. He also has his own sketch show, Souvenir Programme, which in its two series so far has a consistency and sharpness to rival Fry and Laurie on a good day in the late 80s. Nobody writes a tighter sitcom plot or a better-turned gag.
So why isn't he a big star, bouncing on Graham Norton's sofa and releasing disappointing books just in time for Christmas? Partly it might be because Finnemore's intricate plotting and wordplay, and lack of catchphrases, is slightly out of step with modern comedy trends. But the main reason is that Cabin Pressure and the even better John Finnemore's Souvenir Programme are both on Radio 4. You know, the wireless.
"Radio was always where I wanted to do things," Finnemore tells RadioTimes.com. "There's something about doing it on radio, being able to do whatever you like without worrying about budget or costume or filming time, doing it there and then in front of an audience."
Radio allows Cabin Pressure, a sitcom about the staff of a tinpot, one-plane charter airline, to go where Finnemore pleases. "I can have the Scottish cricket team carrying a fire truck across the desert in their swimming trunks – things you can do if you have a multi-million-pound Hollywood budget, or on radio, but nowhere in between. And radio's the perfect place to do visual jokes. You can reveal where people are or who's also listening without it being an obvious pull-back, which it has to be on TV. I like all that."
Finnemore speaks to RadioTimes.com two days after the last live recording for series four of Cabin Pressure, which means he's at the end of eight months of hard work. "The last month, I've been doing nothing else. I stop answering emails and stop seeing friends and hide in my room until it's written. I'm trying to remember what it is that normal people do when they're not writing sitcoms. Or indeed, what it is that I do when I'm not writing sitcoms…"
You can hear the love and sweat that's gone into Cabin Pressure: at its best it's a masterclass in sitcom plotting, with two or three strands airlessly intertwining on the way to a surprising but inevitable climax. "The plotting is always the headache: trying to make things resolve in a way that's satisfying and unexpected. If you've got the plot right, the jokes almost come along with it, I know the characters so well."
The precision of Cabin Pressure's writing is the work of a man who is, unashamedly, a dedicated student of comedy, and has been ever since he spent more of his time at Cambridge in the Footlights than he did working. Finnemore read English, writing a dissertation on Jude the Obscure. "Not full of laughs. At one point, someone throws a bull's penis at someone. That's about as funny as it gets."
Finnemore did also focus on Wilde, Saki and Waugh as part of his studies, but was mainly concerned with practising his writing and performing. "That's where I realised it was a thing that it would be reasonable to have a crack at for a year after university – it wasn't a ridiculous thing for an adult to want to do. There's some stuff I cringe at when I find an old script. But the last show by the double act I was in is one of the best things I've ever done – as is the last panto I wrote and co-directed, which oddly was Sherlock Holmes."
Surely this is worth digging out and bringing to a Cabin Pressure recording? "I've not done that, no. Benedict might look at me a bit funny. It'd be basically, here's some fanfic."
The Footlights' track record for producing future stars is well documented, but Finnemore plays it down. "There are strings of three or four years where nobody went on and did it. It can be a bit daunting: who do I think I am, trying to do stuff for this club that John Cleese, Peter Cook and Stephen Fry were in? Except you're not in the same club as them – you're in the club they were in when they were 18, which is a big difference. Apart from Peter Cook, who was as funny then as he was when he died. But everyone else was learning.
"I was never an academic really. I was always studying comedy at university."
That learning is lifelong: Finnemore admits to sitting in front of TV comedies with a pen and notebook. "I don't understand people who say you can't analyse comedy. Of course you can! You can take apart an episode of Porridge and say, that's how they did it, how clever.
"That famous quote: analysing comedy is like dissecting a frog – nobody laughs and the frog dies. Absolutely true, but you still learn a lot about the frog. It's a good way of working out what makes a frog jump, if you're trying to make your own one. If you are Frankenstein trying to build a frog, dissecting one is a good place to start. This analogy won't sustain itself for much longer."
So what's making Finnemore take out his pen, or scalpel, at the moment? "Twenty Twelve was a fantastic piece of old-fashioned sitcom writing and plotting. Getting On is superb, along with The Thick of It, which I adore. They all disguise how well plotted they are. People love thinking that they're watching slice-of-life comedy – with The Office or even Seinfeld, people will say that what's lovely about it is that nothing really happens, that's just how people are. And I think, no! You can't just show a mundane workplace with someone with delusions of grandeur who wanders about for half an hour. Getting On and The Thick of It do a fantastic job of pretending they don't have a plot or character development, while actually delivering beautiful ones alongside all the naturalistic, subtle jokes."
The Cabin Pressure scripts have to be on a level with the shows Finnemore reveres – he also namechecks Modern Family, Parks and Recreation, Ed Reardon's Week and Bleak Expectations - to do justice to that unbelievably good cast. Despite Cumberbatch's rapid ascent, not to mention Allam's big roles in The Thick of It, Parade's End and the rest and Cole's stints on Coronation Street, Cabin Pressure is yet to lose a member of its original line-up.
"Every series I think, we won't get them all back this time," says Finnemore, who himself completes the show's quartet as dappy flight attendant Arthur Knapp-Shappey. "We'll have to recast or write out one of them. And I wouldn't blame them at all: Benedict's a Hollywood movie star now! He's the main villain in Star Trek! I can't possibly expect him to come along to the Drill Hall and read out my stuff in front of 200 people. But he does! "If one of them's in the theatre they'll do it on a Sunday, on their rest day. It means an awful lot to me. They were pretty prestigious when we first put them together in 2008. I thought, if this were the cast of a new show at the National, that would seem perfectly reasonable. Since then their careers have gone up and up and up."
None more so than that of Cumberbatch – since Cabin Pressure was last on Radio 4, series two of Sherlock has put Cumbermania at an even higher pitch. Has it changed him? "He's dealt with it very well, he seems exactly the same. David, the producer, and I are the ones saying, 'Oh, we've just got a plate of sandwiches from Pret! That's not what you're used to! I hope this is all right!'
"What's different, of course, is the way the audience reacts to him. The first recording we did after Sherlock started, suddenly the queue started very early in the morning, and it was obvious when I arrived for the rehearsal that the demographic had completely changed from the normal Radio 4 comedy audience. I must admit, at that stage I was a bit worried that they had just come to see Benedict. I thought, is it going to fall flat because they're not really interested in the story or the comedy?
"I'd completely underestimated them. They laugh in all the right places and are intelligent and lovely. It was me making lazy assumptions about…"
"As they call themselves! I still haven't quite got the hang of calling them that. We had 17,000 people applying for 200 tickets. People flew in from Japan and Thailand. It's a bit extraordinary. But he's very good at meeting people afterwards and giving autographs."
Cumberbatch's performance is perhaps all the more notable because, contrary to his more famous TV/film roles where he tends to play intimidatingly clever people, in Cabin Pressure he's bewildered loser Martin Crieff, the captain constantly outwitted by Roger Allam as the suave, devious, older first officer Douglas Richardson.
To take just one example from the lines to which Cumberbatch lends his megastar talent in tonight's episode: "All right! The code for the real Ouagadougu is 'Ouagadougu Ouagadougu'!" Or another: "Urgh! Urgh! Urgh! Urgh!"
Explains Finnemore: "Martin's low-status, maladroit, stuttering. But Benedict enjoys playing different parts. He doesn't want to be typecast as a… psychopathic genius. Certainly no-one would use either of those words to describe Martin. He's very uncomfortable in his own skin, whereas Sherlock doesn't even notice his.
"During the recording he and Roger are very spontaneously funny if something goes wrong, or in the way they react to the audience. Roger sort of becomes Douglas, saying things in a very dry, laconic voice. I think, I didn't write that, but that's a really good Douglas line! It is a very Roger Allam role, yes. It's not a stretch for him."
So what, if anything, changes in series four? "There's more development, more things happening in one episode that influence what happens next. I've done a bit more about their stories, in particular Martin's decision about how long he can carry on this odd existence – whether he can carry on working for no money at MJN or needs to go elsewhere. I couldn't keep saying, poor old Martin's got no money and MJN is about to go under. It's crying wolf. People start to think, they are safe really, aren't they? They always have been in the past."
That sounds like preparing the ground for Cumberbatch, finally, moving on. "I couldn't possibly comment!"
Finnemore himself is quietly readying himself to write a third, flawless series of Souvenir Programme. But surely TV has to come calling soon. Anything in the pipeline? "Not really. The possibility of Cabin Pressure going to television has always been around, but isn't actively about to happen. Other than that, no."
There was a near miss recently when a sitcom, George and Bernard Shaw, was canned by BBC1 commissioners having got as far as filming a full pilot episode. "You only have to convince two people that they want it on the radio, whereas you have to convince six or eight people that they want it on the television."
With that project dead in the water – it's definitely defunct, since ITV1's upcoming series Vicious coincidentally has a virtually identical premise – it's back to the wireless. "I'm very happy on radio. Having a sitcom and sketch show of my own is something that still knocks my socks off."
Cabin Pressure returns to Radio 4 at 6:30pm tonight