The name card on the dressing room door says Reverend Wendy Benson, but there is no risk of her interrupting my conversation with Alexander Armstrong and Richard Osman because she is already in the room – as is Sir Peter Moorhouse, who is listed as occupying the room next door.

Crucially, few of the 100 test respondents would know that the cleric and the knight are respectively Osman and Armstrong. The studio audience has to walk past the corridor of dressing-rooms to reach the public lavatories at the Elstree studios where BBC1 quiz Pointless is filmed, so the presenters use the pseudonyms to avoid finding fans of the show at their door.

This intelligence, however, is now pointless because the hosts retired these aliases on the last day of shooting the latest series.

“The Rev Wendy Benson has had a crisis of faith – she’s come out of the Church,” says Armstrong, passing, as he does on screen, a banter baton for his colleague to grasp.

“She’s running a dairy farm in Cirencester,” Osman adds. “It’s a different flock, but it’s still a flock.”

They will choose new door-names before starting the next run, contracts for which were, when we spoke, being negotiated with the BBC by production company Endemol, where Osman doubles as creative director.

Another change of identity occurs in this series. For the 1,000th edition on Monday, the hosts reverse their usual roles: Osman asks the questions and chats to the contestants, with Armstrong at the desk reading the answers.

The pair decided it would be funnier and more effective to make no reference to the switch on-screen. “It was nice sitting down for once,” says Armstrong. “But it did feel weird.”

“And it was enjoyable standing up,” agrees Osman. “It was fantastic fun, but strange. I had done the show so often that I sort of thought I knew what Zander did. But it was so difficult doing his role that it confirmed to me that we are in the right positions. I had to keep turning to him and saying, ‘What’s the thing you say now?’”

The 999 editions they have done with Armstrong erect and Osman seated have followed a template that has scarcely changed since the second series.

While the show was in development at Endemol, Osman and colleagues had played it out in the office around 200 times: “With new quiz ideas, you have to play them with incredibly smart people and then with people who don’t know anything at all,” Osman explains. “And if it works with both, you know you’ve got a very robust format and can potentially make a thousand episodes, which is what you’re always trying to do.”

“The main input I had on the show was very early on,” Armstrong remembers. “I happened to see some of the first series in the gym. I’m very bad at watching my own stuff – usually I see it through my fingers. But I saw this and happened to notice that all the funny stuff between Richard and me had been edited out. And I went back to Endemol and said, ‘Where have all the gags gone?’ It turned out that there wasn’t enough budget at that time for all the cameras we now have. Now we have cameras on each of us.”

To allow more man-chat, the pairs of contestants were reduced from five to four. “That’s when it really took off,” says Osman. “Actually, Pointless goes against all the rules of quiz shows – which are that you keep the recording as tight as possible and make all the episodes as similar as they can be. With this, we shoot it loose and then the big work is done in editing.”

Since Pointless started in 2009, Osman notes, 52 new TV quiz shows have launched and Tipping Point is the only one that he would consider a big success: “Almost all quizzes fail.” Why? “In around half, the format just doesn’t work, a quarter have the wrong presenter, and the rest just haven’t had enough money spent on them.”

Pointless has clearly found the right frontmen. Osman, who was in the habit of playing the presenter when Endemol pitched shows to networks, was asked by the BBC if he wanted to do it for real this time.

Armstrong was suggested because he had just turned down the offer of hosting Channel 4’s Countdown, due to another BBC commitment and the logistics of filming that show in Leeds.

The conceit behind the photoshoot for RT is a “bromance” between the presenters. Do people ever think they’re an actual couple? “It has been suggested on Twitter,” says Armstrong. “But then, so have most things.”

Osman adds, “I can exclusively reveal to Radio Times readers that we’re not lovers. Try as I might, it has just never happened.”

As someone whose day job in TV involves pitching programme proposals, Osman has noted that most major British hits of recent years have been hosted by duos: The Great British Bake Off, Strictly Come Dancing, I’m a Celebrity… Get Me Out of Here!, Britain’s Got Talent. “I think viewers love that sense of a relationship. With Ant and Dec and Mel and Sue, people sense immediately that they’re friends – and warm to that – which I hope is what people think of us.”

They don’t conform to the couple cliché of finishing each other’s sentences, but often add another brick to the pile their partner has started.

When they discuss the coloured column that drops to show how many of 100 people have chosen an answer, Osman says, “Anecdotally, dogs like watching the column going down,” and Armstrong responds: “Newborns stop crying, apparently. It’s very calming.”

As with many celebrated double acts, there is a disparity between the two halves: you could make at least two Madame Tussauds models of Armstrong from the wax for an Osman. But whereas some showbiz duos have ended up communicating only through lawyers, Armstrong insists that he and Osman have never had a disagreement: “Because we do four shows a day and sometimes 50 a month, and it’s entirely unscripted, we have to get on because there are so many times when you rely on the other person having your back.”

A comedy-writing partnership – such as Amstrong’s with Ben Miller – is, he admits, inevitably more fraught: “I have had rows with Ben. It’s difficult when you’re writing sketches. You have to pace around finding holes in the material. And it can’t help but wound a bit when the other person tells you that one of your jokes doesn’t work. So you have to find a way of standing those constant little blows.”

The fact that Pointless contestants also work in pairs is, Osman thinks, another strength: “If you meet one person, you make a judgement of them, but if you meet a couple, your judgements go through the roof. How can they be married? Is he disappointed because his daughter’s a goth? And everyone at home is doing that. So part of the pleasure is in the back-stories.”

The rest is down to the production team, says Osman, who rarely frets about the possibility of having got an answer wrong. “We get people on Twitter all the time,” Osman admits, “but I have never come across a case where they actually proved us wrong.”

“That’s possibly because,” his partner adds, “a surprising amount of people treat Wikipedia as an infallible source.”

The show’s longest dispute was over the county in which stately home Burghley House is. From various historical or geographical perspectives, it’s to be found in Cambridgeshire, Lincolnshire, Northamptonshire, or even the Unitary Authority of Peterborough.

“There was almost a war over that,” recalls Osman. “You may want to think hard about opening it up again on the Radio Times letters page.”

With the current deal between the BBC and production company Endemol ending with this series, might Pointless follow the example of The Great British Bake Off and defect to another network if the cheque were tempting enough? 

Osman is emphatic: “I think Pointless is a BBC show, and will remain a BBC show. Look, we live in a very different TV environment now. The move of Bake Off [to Channel 4] I understand, The Voice UK [to ITV] I understand. But there would be no commercial reason to move Pointless, and we'd never want to because the BBC have backed it from day one – from BBC2 to BBC1 and to Saturday-night specials, they’ve looked after it.

"I think we have a duty of care to the people who watch it on BBC1 to say we’ll do it on this channel for as long as you want it.”

One of the lessons of the Bake Off move was that many of TV’s biggest shows are now owned by the people who make them rather than the networks that screen them.

“The BBC used to be a huge production powerhouse, and now isn’t so much. Most of the independent production companies are run by ex-BBC staffers. But the big story is that ITV is now essentially what the BBC used to be: a series of production companies that they own and commission through. It’s now very hard for an indie to get a show on ITV, but much easier to get one on the BBC. Which is a complete reversal of how it used to be.”

Osman examines the ratings every day. “I’m always looking for cracks or even the beginning of a crack. Are you down by a percentage year on year? Have you come up against another show that beats you? There hasn’t been anything yet.”

I mention that, in my only conversation with the great reclusive artist Lucian Freud, he said that he enjoyed watching Pointless. The hosts are delighted but not entirely surprised: they have been told that other fans include Dame Judi Dench, ex-England manager Roy Hodgson, writers Jimmy McGovern and Robert Harris, Lord Kinnock and the Queen.

“A Palace insider told us that she watches it,” confides Armstrong. This might make him hope for a knighthood, except he has already been ennobled as Sir Peter Moorhouse, to whose dressing room he now returns. Neither should prayers from Rev Wendy Benson be necessary to give Pointless a chance of reaching 2,000 shows.  

Pointless is on 5.15pm weekdays, BBC1