While some trends in television come and go, quiz shows remain and are at the centre of ITV's latest bid to woo back lost viewers. But who thinks up all the questions? We track down the "friends" you would really want to phone.
By Jonathan Duffy
BBC News Online
Fittingly for a firm which writes questions for some of the toughest quiz shows on TV, there are few clues to Century Quiz Promotions' whereabouts.
Even as you stand on the front doorstep of the anonymous terraced house which contains the offices, there is nothing to announce this as the intellectual hub of some of Britain's hottest television property.
A budding Loyd Grossman might take one look at the exterior - the peeling paintwork, the weeds peeping up from the pavement - and dismiss it as a typical student hovel.
Ironically though, there's no shortage of students who would be prepared to trade their entire cheap beer entitlement for the keys to this place.
The unlikely intellectual hub for Britain's top TV quiz shows
This is where the questions to some of Britain's most popular TV quiz shows, including that enduring arbiter of academic prowess, University Challenge, are thought up.
Whenever the show's host Jeremy Paxman fires off a trademark "starter for 10" he is reading from the hymn-sheet of this remarkable little company based in Liverpool.
Likewise, with the BBC's recently resurrected Mastermind, it is Century which sets the questions.
Almost since the dawn of television itself, quiz shows have commanded huge audiences.
The genre has evolved of course, formats have become increasingly ludicrous and the prize money is measured in millions now.
But you can't have a quiz show without questions, and Century is the production line that feed this voracious beast.
Started in 1984 by former Mastermind semi-finalists Janet Barker and Neville Cohen, the company has done a profitable line in supplying questions for dozens of TV quizmasters.
Trivia queen Janet Barker in her office
As well as the highly regarded University Challenge and Mastermind, it currently has a handful of other top shows on its books, although it can't say which.
Recently it has expanded, launching a website that instantly supplies questions for pub quizzes.
Beyond the front door of Century's curiously domestic business premises, the shelves resemble the reference section of a well-stocked local library.
Berlitz travel guides nestle next to old editions of Whitakers Almanac. "Who's Who in World War II" jostles for space with sports year books, movie guides and biographical dictionaries.
Check and double check
The front room is home to Neville and fellow question setter Ray Oakes, a veteran of local quiz leagues.
Next door, is the "sitting room" where Janet is based. They are all sticklers for accuracy, she explains. Each answer must be doubled sourced and all go through an independent verifier.
"Even the Encyclopaedia Britannica gets it wrong sometimes," says Janet. "Like it says there are 31 jumps in the Grand National when there are only 30."
Down the years, the company has built up a database of 43,000 questions it can call on and adapt for various shows.
But they continue to write new ones. On a good day, Ray will come up with 40 to 50 questions.
"It's difficult to say how it works exactly. You just have to come up with ideas and then go to a source to see if they're right."
There are some guidelines. "Anything that begins 'why' is not a good question because there would be so many ways of expressing an answer.
Questions under lock and key
"A good question is one that gives you a clue to the answer. So you can make an educated guess."
Janet chips in, "a member of which brewing family was the first lord mayor of Dublin in 1847? You could make an educated guess and say Guinness, and you'd be right".
Janet Barker formed the company after Mastermind in 1981
Not all questions can be that easy of course, especially not when big cash prizes are on offer. But as the stakes have risen, so has security.
When Century wrote questions for some of the early Who Wants to be a Millionaire? shows, they were saved on a floppy disk, and couriered to London under heavy protection. But even that became too risky for the programme makers Celador, which has since taken the contract in house.
Such issues are not a concern with Mastermind, in which the top prize is kudos rather than cash. But the more populist specialisms permitted in the new series, including The Simpsons, The Who and British TV comedy 1970-1990, has led to charges of dumbing down by the BBC.
Be my friend?
Janet - who puts her knowledge down to a "bloody good memory" - confesses she is split on this issue.
"People learn different things at school these days. No one learns the kings and queens of England by rote but they know astonishing amounts of stuff about the second world war.
From these books come some of TV's quiz show questions
"But I think it's sad people don't understand classical references as they once would have."
Quiz shows have changed immeasurably since Janet first tasted success, winning the 1977 series of the BBC teatime favourite, Ask the Family.
Given her talents, isn't she tempted to pack in the work and clean up in some of the big paying TV quizzes of today?
"I feel tempted certainly, but we couldn't do [Who Wants to be a] Millionaire because we've written for that."
Could she at least be listed a friend to phone for anyone going on the show.
"I don't see why not. I've been asked before, but they've never got that far."
How much do you know about TV quiz shows? Try these five questions set by Janet and the team.