Have you heard the one about the adult education class where everyone in the room thinks they're a comedian? Hell on earth to most teachers perhaps, but for tutor Chris Head that's exactly what he's hoping for.
Chris's course - Innovations in TV and Radio Comedy - might have a serious-sounding handle, but cracking jokes and making laughs is what it's all about.
Each Tuesday night, his students gather at the City Lit in central London, searching for inspiration in the classics of comedy that will help them develop and improve their own comedic work. Short video clips are interspersed with exercises, performances and improvisations. Funny lines that emerge from the class are worked up into full routines for homework.
Having invited myself along to watch a typical session, I soon discover that "watching" isn't quite what Chris has in mind for me. "Journalist? Don't make me laugh," his deadpan look suggests, as he propels me up from my chair to join in with the dozen or so regulars. Ouch! Sitting on the sidelines and quietly carping at other people's efforts is one thing: having a go yourself is quite another.
For the warm-up, we all have to circle the room, leading "in a funny way"
with different parts of our bodies. Chris calls out the changes: hands, knees, elbows and bums. It might look easy when Charlie Chaplin or John Cleese gyrate their way across the screen, but getting a laugh out of your funny bone takes some doing. Next, we're off on a hunt for this week's "comedy basic": the highlow juxtaposition.
The students are a bright bunch, but this leads to a collective scratching of heads. Yes, we're thinking as it sinks in, comedy really is a serious business. After a few minutes, I think I've spotted said juxtaposition, buried away in a Stephen Fry monologue Chris is showing us on video.
"Oooohh," chorus my colleagues in comedy, followed by a chant of:
"Teacher's pet, teacher's pet." I don't care. I may not have hilarious elbows but at least I've got something right.
Silly names, our teacher tells us, are making a comeback, so he puts us into pairs to come up with some of our own. I work with Mark, a bearded forty-something with an impish look in his eye and an underlying tinge of sadness that tells me that he really does want to be a comedian.
Mark tells me that in "real life" he's a company director, then, two minutes later, that he earns his living from labouring. I can believe either. His middle name, he reveals, is Olivier, because, on the day he was born, his father sold a picture to the late, great thespian.
The idea is that we take the other person's initials and create an amusing name to fit. I hand him Man-hunting Oft-bedded Harridan, and receive Strictly-a-paedophile Judderbuttocks in return. I also manage Mercurial Orange-eating Hamster and Mellifluous Officer Humbug. Well, it seemed funny at the time.
Now we get to find out who's done their homework. It's refreshing to discover that, in one respect at least, this class is no different from any other. Out of the six men and four women present, only three have written the piece they were set the previous week.
First up is Gary (names have been changed to protect the guilty). He presents us with a snappy little dialogue where on the surface he's buying food, but what he's really looking for is a dirty video. The punchline: toad in the hole.
Jim too has a written a two-hander, but chooses to read both parts himself.
It's good - full of pain and pathos - but it's not funny. Neither is Neil's piece about a washing machine. It could be, but he fluffs the punchline, then unwisely carries on for another 20 seconds or so, not realising that he's missed the laugh.
Can you, I ask Chris during our break, actually teach people to be funny? "No," he says straight away. "They need to be funny to start with. But you can hone and polish and improve on what they've already got."
And the analysis of the work of others, where does that fit in? "Comedy is spontaneous and unthinking," he says, "but if you've analysed it then it's already prepared your mind, setting up certain pathways in your mind."
Naturally, Chris is a comedian himself. Working under the stage name Tobias Fortnight, he's the regular compere of a stand-up show at the Arts Club in Soho. He's also written for Radio 4 and Radio 1 and taken several shows to the Edinburgh Festival.
In a former life, he worked as an administrator at the City Lit. But after taking a course there that looked at the development of modern art, he thought: why not do the same with comedy?
That was back in 2001. After various trials, he hit upon his current format, working his way from 1960 - "the last year the Goons were on television" - to the present day. The class has proved popular and there's a long waiting list every term.
Back in the classroom, it really is time to put up or shut up. Paired up again, we work on improvised sketches revolving around puncturing the egos of self-important and pompous characters.
This is tough. There's a tight deadline and our one imperative - to be funny - suddenly seems like the hardest thing in the world.
One by one - two by two - the other pairings do their bits. Then it's our turn.
We've come up with an improbable routine about stationery salesmen at a conference and their great new invention: the T458LS47 paperclip. We stride about the room declaiming. The punchline comes and goes without anybody noticing. The sketch dribbles to an end. Nobody laughs. Ah, well, there's still the day job.
Chris sets this week's homework. I decide not to write it down. If I come back next time, I'll have to stump up the fee for the 12-week course - pound;180 - and there really is nothing funny about that!
"Innovations in TV and Radio Comedy: 80s and 90s" is at the City Lit, Keeley Street, London WC2, www.citylit.ac.uk