While they worked together on the likes of Chewin' The Fat and Still Game, the pair ate together, holidayed together with their families and lived out of each other's pockets and homes. But then in 2008 they fell off the mountain that was monumental success, in Scotland at least, when Hemphill decided he wanted out: out of their writing partnership, their production company, and in effect, out of each other's lives. The result was seismic; new BBC sitcoms were cancelled, the expected Still Game series was still born, and the pair didn't speak - except for business or legal reasons - until a few months ago.
Today, however they're sitting in a comfy room of a swish Glasgow hotel talking about their return to Still Game in the form of a 21-night stage show at The Hydro in the city. And while they are not quite wearing matching stetsons again, metaphorically, the laughs are flying around like lightning bugs at a campfire.
Cynics, however, will suggest the partnership is a marriage of convenience, with the minister being the agent who's pulled together The Hydro deal that will see them play to almost quarter of a million fans, grossing more than £10 million.
"That's sh***," says Kiernan, straight-faced. "We didn't come back for the money. We wanted to see if people still wanted us." Hempill agrees: "Everything's fine between us. We're back in the right place. And if people understood our friendship they would know that it never did get that bad."
For the next hour the pair reveal why this friendship was a third party so strong they simply had to reconnect. And surprisingly, a packet of Walker's beef crisps, "wi' the corrugated ridges", played a symbolic role.
"Both of us hold receipts for payments from 1989 when we appeared in Blackfriars' pub [in Glasgow] doing stand-up, and we got a tenner," recalls Kiernan of their first awareness of each other. "Then Bruce Morton, who was my best man, introduced us. Not long after, me and Greg turned up at Morty's flat at the same time to celebrate his 40th. But as he opened the door, the chain was on, and he indicated he was 'indisposed'. So me and Greg decided to go to Cottiers bar for a pint."
That was a defining moment in the relationship. "Greg offered me one of his crisps. But I'm no' disposed to taking somebody's crisps out of their poke - it's just something I don't like - I'd never take food off someone's plate, but something in my mind let me take one of these beef corrugated crisps."
Hemphill wasn't aware of his new chum's minor OCD, but he did realise there was a connection. "We got on like a house on fire," he recalls. "And we talked about the comedy business of the time. We both loved Jewish humour, movies, American culture."
The new pals, on paper, had little in common. Kiernan grew up in the east end of Glasgow in a single-parent family, living under a glass ceiling as close as the thin walls. "The careers teacher said to me: 'Kiernan, your options are plain and simple; the egg boxing plant, Marshall's Chunky Chicken, or you could try humphin' coal'."
Hempill grew up, for the most part in Montreal, Canada, in a middle class family and attended a school that looked like the one in Glee. "My teacher at high school said I should do more acting," he recalls.
Kiernan sped through a variety of jobs on leaving school, from warehouse worker to car exhaust recycler while Hemphill returned to Scotland to take an honours degree in theatre, film and television at Glasgow University - where Kiernan had once been a barman.
Yet, while both loved the laughter business, they didn't become a comedy couple straight away. Kiernan formed a double act with John Paul Leach while Hemphill had two partners in the Trio Bros act. The pair did come together, so to speak, when they became involved in the sex industry.
"I was running a call centre at the time which handled sex chat lines," Kiernan recalls, smiling. "Comedians and actors such as Bruce Morton, Stu Who? Jenny McCrindle and Greg all did stints."
Hemphill grins as he recalls the unlikely world. "Our job was to monitor the calls to make sure the callers didn't exchange phone numbers, and phone each other independently. And make sure things 'didn't get too out of hand'. We were professional eavesdroppers."
The pair's attempts to break into comedy saw them leap through several hoops; writing for other people, quiz shows for television. In 1994, Hemphill presented sports show Off The Ball and both worked on Channel Four's quiz show, Space Cadets, with Star Trek's captain, William Shatner.
"We both enjoyed working with him," says Hemphill, grinning. "But every time he bent his head down to read the script we'd look at his head to see if we could see the weave."
In 1995, the pair heard of The Comedy Unit's plans to pull together a team of performers to write and perform a new sketch series, Pulp Video.
"TV shows were like the last helicopter out of Saigon," says Hemphill in dramatic voice. "We were all waving our passports in the air. We had to be on it."
The likes of Jane McCarry (the future Isa in Still Game), Julie Wilson Nimmo ( the future Mrs Hemphill), Gavin Mitchell (the future Boaby the Barman in Still Game) were among the passport wavers.
"The show was hugely populated, and it was tough," says Hemphill. "Everyone was fighting to stay in it, to get noticed. There was no camaraderie, we would all have slit each other's throats to get on that helicopter. Yet Ford and I were never in competition. I guess it was because we did different things."
Kiernan concurs: "We were tight as a drum, bevvying together, and in each other's pockets," he says. "We formed a real big friendship. And during the run we wrote some sketches together."
One of the sketches featured Hemphill and Mitchell playing two old men. "This sketch set something off in me," Kiernan recalls. "I remember going to director Ron Bain and saying I'd really like to play an old man in the show. I mentioned it to Greg and it was then we came up with the Still Game characters, Jack and Victor, with Gavin [Mitchell] playing Winston. Somehow, we knew we could write for these characters."
They just knew that when Pulp Video was broadcast they would be in demand from every corner of Televisionland. "We were in the pub that night the show went out, assuming we were all ready to be stars and actually having this hypothetical conversation asking if EastEnders or Coronation Street offered us a part would we take it," says Kiernan. "We both said 'Naw!' We'd hang out for the big comedy stuff."
Hemphill sums up what happened to Pulp Video. "Nobody watched it. It wasn't a bad show, but we'd figured Pulp would last four or five years. We thought we'd arrived but the journey had only just begun."
The show didn't work, but the shared experience, even the pain of disappointment solidified the friendship. But Pulp Video gave them more; they believed they could go it alone. "We felt our stuff was the best in it," says Kiernan, being honest rather than arrogant. "We felt we could do our own show."
Meanwhile, they were more skint than a clumsy schoolboy's knees. What to do? To paraphrase Dr Johnson, 'the thought of being hanged in the morning concentrates the mind wonderfully to come up with a play.' The comedy pair returned to the well that was their old men characters, developed during chats about Hemphill's uncle Sammy and Kiernan's uncle Barney.
"We wrote it in ten days," says Kiernan of the play. "When writing we spoke as the characters and then wrote down what we were saying." Hemphill continues; "We called it The Bunker, because this little council flat seemed like a bunker. Then we asked Karen Koren, who runs the Gilded Balloon in Edinburgh, to put it on at the festival, and she agreed, but said 'The title is s***, guys. Call it Still Game."
The summer of 1997 was a hot one as Kiernan, Hemphill and Paul Riley as Winston (Gavin Mitchell was in another festival play) pretended to be old men huddled around a one-bar electric fire in the middle of winter. But as the white make-up ran down their faces, tears of laughter ran down the faces of the audience. The show was such a success, Karen Koren produced it in Toronto. So it was only a matter of seconds before BBC Scotland took their Pulp Video performers and turned the new stage show into a sitcom?
"That never happened," says Kiernan with a shrug. "But LWT came to the festival and bought the rights to it. They had the idea of starring Derek Jacobi and the Irish actor David Kelly as the old guys, with us writing it." (Network wouldn't take a chance on three younger unknowns playing old guys.) After three years, the rights expired. "We got a couple of grand for the rights, and we were pleased someone had loved it." Another false dawn? "Yes," say both in unison.
However, when the Comedy Unit heard BBC Radio Scotland were looking for a laughter show, they suggested Kiernan and Hemphill. The result was Chewin' The Fat. The duo heard the fantastic news when they were at the airport, set to take off to Faliraki on holiday with partners Lesley and Julie. "What a f****** great flight that was," recalls Kiernan, grinning.
But why drop the series after four seasons? "We had begun to dislike it," says Hemphill, honestly. "It was tough to keep it fresh. We also knew we wanted to write a sitcom, but the Comedy Unit weren't keen."
Their determination paid off and BBC Scotland paid out for a Still Game pilot. But it sat on a shelf for a year due to budget restrictions before being aired. "Aye, but you could get it at the Barras," says Kiernan, laughing at the ingenuity of Glasgow's market stall entrepreneurs. "Somebody had bootlegged it and sold it and punters were watching the new TV show before it was even announced."
During the wait, the pair were still rubbing Germolene into their knees so they came up with a flash of entrepreneurial genius themselves. They filmed a performance of Still Game, the theatre show, at Cottiers in Glasgow and put it out as a video. They sold 13,000 tapes straight away. It was another indication Still Game was comedy gold. And so the sitcom ran for six great seasons. And the nation laughed 'till it hurt. But then Hemphill, citing the pressures of business and deadlines, announced he did do walking away.
The divorce had its share of acrimony. Right now, it's awkward. The pair go silent, reflecting. And it's understandable. However, Kiernan lightens the moment. "Trial separation!" he says, smiling, recovering. "Love is always lovelier second time around."
Hemphill joins in, grinning; "Burton and Taylor - that's us." Maybe not a great example, given they failed ultimately but...but if they could go back in time, what would they have done differently?
"Probably go slower," says Kiernan. "At the time we were looking at everything; new formats, new shows. And we were completely in a phone box. We couldn't get away from each other, plus the output was so heavy."
Hemphill nods in agreement: "It was also to do with frustration. We had a hit show but it wasn't treated well by network." Was there a sense they'd also become so big they were affected by their success? "It wasn't that," says Hemphill. "I felt if we'd done series seven of Still Game it wouldn't have been a great show. And the demands of TV would have caused us to burn out."
Kiernan thinks for a moment then says: "You know, that's right. It's the first time it's been said but it's true. We'd gone down the route of setting up our own production company, to try and follow the likes of Mel Smith and Gryff Rhys Jones, and sell it. But we tried too hard."
After the split, Kiernan locked himself in a room and wrote a play for Glasgow's Oran Mor theatre, partly because his partner had already written one. Did Hemphill go see his ex-partner's effort?
"Naw, he never came," cuts in Kiernan, laughing. "Because we weren't talking at the time. Although there was a man at the back of the hall with a moustache and glasses I think might have been him." Hemphill laughs: "It wis' me, with the Groucho Marx outfit!"
The years passed. The pair talked. The awkwardness dissolved. "Time helped," says Hemphill. "And I was frustrated at seeing inferior programmes come out of London."
"Yes, we had dialogue," says Kiernan. "Bits and bobs. Then one day last year Sanjeev (Kohli, Naveed in the show) was asked to do something in character, and we owned the character, so we discussed that. Then we got to talking about The Hydro, and we agreed we wouldn't want to end our careers not having stood in front of a Hydro audience." He muses: "And comedy these days is a stadium gig."
The death of Kiernan's 12-year-old son, Sonny, later reinforced the belief that life is all too short for grudges. (Hemphill and his wife flew straight back from LA where they were living on hearing of the tragedy.) Kiernan was devastated by his family's loss and, almost unbearably sadly, he took to Twitter in June on what would have been his son's 13th birthday to write: "Happy Birthday Sonny! A teenager today!" In the midst of all that, while putting together the show, his mother Frances passed away.
But what of their future. The pair reveal they are in talks with the BBC about a new series of Still Game but this time they don't want to be dropped on to BBC2 at a time when people are putting the cat out. They also want a deal with Australian TV, following the Mrs Brown's Boys lead. "We'd love to take this new stage show and tour Australia with it," says Kiernan. "We think it's good enough."
This time around though they'll go about it differently. "We feel we can be in control of what we were doing," says Hemphill. "Plus, we really missed the characters. They were people. We wanted to see them again, to take up where they left off."
How was it sitting down together to write for the first time after their years apart? "It was a bit odd," Hemphill admits, with the awkward 'Hi, how are you?', and all of that." Kiernan cuts in, smiling: "Yes, but I brought a packet of Tunnock's Tea Cakes and we got tore into them. Then we watched the old episodes of the show to get back into it. And when we hit the keyboard, the words came out like an explosion."
What of the new stage play? What's the premise?
Kiernan replies, laughing: "You can f*** right off! We're no' even telling the cast until they come to rehearsals. We want it to be a surprise for the audience."
And his chum agrees with the plan, the pair off them now laughing like a couple of drunk cowboys telling jokes over a bottle of Jim Beam and a mountain campfire.
Extra seats have now been released for the shows, running from September 19 for 21 nights, at The Hydro, Glasgow.