Steve Coogan was out for a meal last night, and this morning, while we talk on the phone, Twitter is lighting up with excited chat about his dinner companions. A photo posted by the actor David Schneider shows a smiling group shot: Schneider leaning in like any selfie-taker, surrounded by the grinning faces of Coogan, Chris Morris, Rebecca Front, Doon Mackichan, Patrick Marber, Peter Baynham and Armando Iannucci. “We’d not sat down in the same room for 15 years, so we all met up and had dinner. It was jolly nice, actually,” says Coogan.

Marber decided the 25th anniversary of their groundbreaking news parody, The Day Today, deserved a celebratory dinner. But the get-together was more than a chance to reminisce, as the talk turned to work projects and the possibility of a reunion. “Yeah, we said we should do something,” says Coogan. “Everyone has gone off and done their own thing. But 25 years is quite long enough to prove that you can do something else. So we may do a podcast or something … I don’t know.” But this wouldn’t be for old times’ sake. None of the team that wrote and performed that excoriating, angry comedy is looking to rehash the past. “There’s no point doing anything that is just based on nostalgia,” he says. “Because what we did was very edgy and challenging. You either do something equally relevant or don’t bother.”

A quarter of a century after Coogan’s clueless sports reporter turned broadcasting pariah, Alan Partridge, made his screen debut on The Day Today, he is returning to the BBC in This Time With Alan Partridge. The conceit is that the disgraced anchor has been invited to cover the absence of the regular presenter of a One Show-style magazine programme. Despite Partridge’s deep-seated loathing for the “BBC gravy train”, he has been in the digital radio wilderness for years, and is desperate to get back in front of the cameras. Luckily, the BBC, wanting to reflect the voice of little England in these politically altered times, thinks Partridge is just what it needs.

Facebook Twitter Pinterest Coogan as Partridge in 1994. Photograph: BBC

As Partridge fans will remember, he left the BBC under a cloud after shooting one of his guests dead with an antique pistol during an interview on his prime-time chatshow, Knowing Me, Knowing You. His subsequent, desperate attempts to gain a second series ended in ignominy when he thrust a wheel of cheese into a BBC commissioning editor’s face, instructing him to “smell my cheese” before fleeing across the car park.

The new series begins with Alan in lime shirt, mauve tie and navy blazer, next to his co-host Jenny (played superbly by Susannah Fielding), preparing to go live to the nation. As the gallery counts down to transmission, he smacks his dry lips repeatedly, shot in closeup like an Ingmar Bergman character, and asks for water. No one hears him as the pre-air bustle goes on around him. He bares his dry teeth, like a monkey watching a hunter’s sights line up with his eyeballs. It’s all in the eyes. The terror.

The series is shot in a windowless studio in south London, which Coogan swears has left him with a vitamin D deficiency. “Seasonal affective disorder while dressed up as Alan Partridge is not good for your mental health,” he says. The intense filming days on the cheery red-and-purple studio set are peppered with occasional laughter as Coogan comes up with gags on the hoof, alongside his co-writers and directors, Neil and Rob Gibbons. Twins, but physically unalike, they are brown-haired thirtysomething men in T-shirts and trainers. They keep a low profile. I don’t hear them speak until a tea break, as they communicate in mutters, directing the action like taciturn snooker commentators. While one of them paces and studies the monitors, the other sits glued to a laptop, changing the script as they go.

In a break from filming, Coogan comes over to offer a handshake, eyes weary from the concentration of take after take, trying different emphases, searching for the perfect line rhythm. That incredibly finicky needlework he is doing with his co-writers is the norm. Every beat of the script is picked over, pulled tighter and trimmed while the cameras wait to roll. It’s like watching them all bent over a tapestry, producing a single square inch a day. “It’s tiring,” Coogan says, flexing his left hand like a golfer warming up for a putt.

Facebook Twitter Pinterest ‘It’s a bit Das Boot in here, isn’t it?’ … Partridge in full flow. Photograph: BBC Studios/Andy Seymour

I ask him what his lapel badge means. It’s a small, white tooth; a molar, with a cartoon face drawn on it. It represents a shadowy showbiz organisation not unlike the Freemasons that “looks after” its members while doing philanthropic works. It may never get a mention in the script, he says. But it’s all been worked out and is authentic to the character. I still don’t know who is telling me this, Coogan or Partridge. In full wig and costume (he says it takes less makeup these days), he is hard to pin down. Neil Gibbons admits both brothers have had conversations with him where they are unsure who they are talking to.

As he is explaining the lapel pin, the just-visible join between Coogan’s toupee and his forehead is the only reminder that Alan is fictional. In the strange, hermetically sealed world of the studio, I have to remind myself I’m listening to an actor in a costume. It is amazing to watch close up. The enjoyment he takes in conjuring Partridge’s prose, even after a long day, is palpable. “It’s a bit Das Boot in here, isn’t it?” he jokes. A little laugh ripples through the crew.

He is not, as I had expected, a performer grudgingly putting on the blazer and slip-ons because it is what his audience demands. He has long since passed the point where he needs to be Partridge for exposure or money, with Oscar and Bafta nominations cluttering his inbox. So why keep coming back to him?

“Well, I suppose the simple explanation is that it makes me laugh,” he says. During a take, the quietly focused brothers – “Like hired comedy killers,” he says – will do that silent knee-bend, head-back laugh when Coogan pulls off another bit of business that gives the scene a new moment. The collaboration is total. When something doesn’t work, Coogan defers to them as if they’re Stanley Kubrick, not two young comedy writers he hired to turn in some Paul Calf gags for a TV pilot that never got made.

Despite Partridge’s flaws and after living with him all these years, Coogan has a real affection for him. “For me, it’s this strange, long journey, but it has been very good because I’ve had this sort of love-hate relationship with Alan. I’ve come to accept Alan in my life.”

He can dip in and out of Partridge thanks to his co-writers, who have kept the crucible bubbling between TV projects, writing books in that incredible, deluded voice and Alpha Papa, the big-screen Partridge transfer that saw him taken hostage by a disgruntled co-worker. The brothers joke later that their work schedule with Baby Cow, Coogan’s production company, featured no days off at all “apart from Christmas” for the next few years, until they pointed out they would need some time away.

But their working relationship is a unique one, and one Coogan says he wouldn’t be without. “I was in the makeup chair, and I looked up at the makeup artist, Lisa Cavalli-Green, and I said: ‘You do realise, Lisa, that you and I are the only ones left?’” She was Partridge’s makeup artist back in 1994. Coogan ploughs a lonely furrow, like Partridge forging through the Norfolk countryside with a big stick and a meaningful look in his eyes.

He’s not stuck in a sort of weird Enid Blytonesque cast like Jacob Rees-Mogg Steve Coogan

When he found the brothers, originally from Cheshire, now settled with young families in Manchester and London, he struck gold. Several times he heaps praise on them for the new layers they have found in the character. “I remember it was like a little epiphany when I went through the material because I was clutching round Armando, Pete and Patrick, thinking: ‘Which of you three will help me do something with this character?’ Not any fault of theirs, but Patrick and Pete clearly wanted to get out from under the weight of this big, heavy albatross and go away and do their own thing. It’s a kind of millstone of sorts.” You can really, deeply love someone, but want them to go on holiday once in a while. Give you your space back.

“There was no one around to help me write Alan. I was sort of left holding the baby.” It quickly became obvious that the brothers weren’t just going to satisfactorily adopt the house style; they’d bring Alan a whole new complexity. “They aren’t just keepers of the gate,” Coogan says. “They have moved the character on, undoubtedly, and made it more sophisticated.”

But timing is everything, and the alchemy that sees Partridge back at the BBC on the cusp of such huge national change couldn’t be more perfect. Like King Arthur in Avalon, he waited for his time to come. And come it has.

Although the show doesn’t directly reference Brexit, because it’s a train that is moving too fast, and they’re not in the business of political satire, it hints at the current divisions over everything from gender politics to the #MeToo movement and lets Partridge grapple with them.

Coogan says Partridge’s lack of a mental gatekeeper is the gift that keeps on giving. “The way I’m talking to you now, I’m being careful about how I’m phrasing things because it’s me talking. But as Alan, you can sort of let the dog off the leash.” And off it runs, knocking over tables and soiling the studio floor like a Blue Peter elephant.

Just as Coogan sits looking at Partridge in the makeup mirror, noting the changes in his face, we sit at home watching Partridge reflect the changes in our cleft homeland. “Alan understands how to be socially progressive. He’s not stuck in a sort of weird Enid Blytonesque cast like Jacob Rees-Mogg. He makes an effort with the evolution of gender politics and social liberalism,” says Coogan. It’s his “making an effort” that is the source of so many laughs. “The world has slowly realigned itself with Alan, and Alan has slightly realigned himself and made himself a bit more palatable.”

He’s not a kneejerk bigot, but someone trying to appear “woke” despite his internalised prejudices. He says all the wrong things and doesn’t know when to quit a line of questioning, but by God, the effort he’s putting in is total.

Of the zeitgeist, Coogan says that Partridge “understands it, or half understands it, and knows he needs to go with the flow and not kick against the pricks. Even if it’s only cynically for career reasons.”

While the writers acknowledge that the TV host embodies many of the qualities of a leave voter, he is too much of a “magpie” to stick to a single ideology. He’d much rather borrow soundbites from other soft Tory figures, such as Michael Gove or George Osborne.

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Coogan says they had some lively discussions about who Partridge now aligns himself with. Who has he heard talking about the big issues and agreed with lately? Coogan warms to this. “There is a quote in episode two where he says there is evidence that lower wages increase productivity.” He goes on, more Partridge now than Coogan: “As Kirstie Allsopp says: ‘A well-fed dog is a lazy dog.’ The thing is, Allsopp never said that at all, but we have fun with things like that.”

Libelling Allsopp aside, Partridge is trying to keep his nose clean and make a good impression. This time, he’s back, he says, to “give of my best”. He’ll cock it up, obviously, but he really is trying.

This Time With Alan Partridge starts on BBC One at 9.30pm on Monday 25 February

• This article was amended on 19 February 2019 because a photograph of Steve Coogan playing Alan Partridge on The Day Today was captioned as 2002 when it dated from 1994.