“WHEN I started at drama school there were nothing but working-class people. Peter O’Toole, Albert Finney. Tom Courtenay. There wasn’t a posh boy there.”

Diana Rigg – Dame Diana Rigg if you want to stand on ceremony; she doesn’t insist on it – is sipping prosecco in the bar of the Groucho Club in Soho. We are discussing issues of contemporary class representation in her chosen profession.

“It’s swings and roundabouts,” she continues. “And we just happen to have a lot of very talented boys who have been to public school right now and it will even itself out next year, the year after. Why make a fuss about it? They are extremely good actors. If they weren’t there would be a point to the argument. But there is no point to it.”

Really? In this Cumberbatchian age we live in one wonders if the likes of Finney would get a foothold now. When grants are a distant memory would he even have got to drama school?

“I think if you want something you will chase it,” chips in Ruairaidh Murray, an actor himself, though not of the public school variety (Stockbridge Primary School and Broughton High School if you must know).

“They will get there,” continues Rigg. “They will get there. They’re not put off by seeing an Etonian there. Why would they be?”

It is an afternoon in early July. The Groucho Club is humming with life and conversation and alcohol (though in the interest of full disclosure, of the three of us only Rigg is partaking). We are gathered here today to talk acting and Edinburgh and love and growing old with two actors at very different stages of their careers, linked by a love of acting, by the Fringe and more tangentially by their Scottish histories.

Murray is 40 (which is news to Rigg: “Hello! You don’t look it”), puppy-dog eager and still a fresh face. He has been a regular at the Fringe in recent years and is returning in August with a new two-hander, The Club, which, as with previous shows Boxman, and Big Sean, Mikey and Me, he has written himself and which mines the same strain of coal-black dark comedy as they did (“Phoenix Nights meets The Sopranos” is the tag-line).

Murray has done his share of small parts on TV over the years from The Bill to Bob Servant and he also has a role in the new season of historical drama Borgia (not to be mixed up with The Borgias, of course. That’s an entirely different take on bloodthirsty Italian renaissance history).

As for Rigg, well what could you possibly need to know that you don’t already? Famously she played Emma Peel in The Avengers back in the day (repeats most nights on the True Entertainment channel). She’s been one of the most highly regarded stage actresses of the last half a century. She’s married James Bond (in On Her Majesty’s Secret Service; it didn’t last) and solved crime as the eponymous heroine of The Mrs Bradley Mysteries. She once had her own American sitcom called Diana (you can find it on YouTube), made guest appearances in Doctor Who and The Muppets and of course is currently one of the stars of some minor, trifling TV show called Game of Thrones.

Oh and she’s also Rachael Stirling’s mother (they’ve played together in both Doctor Who and Detectorists), lived in Scotland for years while married to Rachael’s father, her second husband, Archie Stirling (they divorced in the wake of his affair with the actress Joely Richardson though that, as we will learn, is not something she dwells on now).

And yes, she was one of my teenage pin-ups. Her and Jenny Agutter. (I’m of an age.) Even at 78 she still has the cheekbones. Back in her Avengers days boys would send her letters. Her mum would reply for her. "She would write back and say, ‘My daughter’s far too old for you and what you need is a good run round the block.’”

She’s even done the Fringe herself. Indeed, that’s why we’re here today. A couple of years back she did her own Fringe show, No Turn Unstoned, about the bad notices actors have received.

“And miracle of miracles,” she tells me, “I made a profit. So I thought what I’d love to do is – because I saw all round me kids doing stuff they’d probably mortgaged their mothers to do – is recycle my profit.”

So she went and saw as much as she could and gave money to her favourites. And as it turns out Murray was one of them. “I got a note,” he recalls, “which I was obviously highly excited about, flattered and maybe blushing a little.”

What did the note say? “I think it was just 'congratulations'.”

“No, no,” Rigg butts in. “I said you should play something slightly differently.”

“Oh yes. It was to do with the mum character. I did take that note on."

Do actors like getting notes, I wonder? “Well I do," says Rigg. “The point is: if, as an actor, I go and see a show and I think the note is valid, then I must [give it]. It’s not about power. It’s about sharing my technical knowledge with somebody younger than myself. You can accept it or not accept it. It’s not a command. You can just go away and think about it and dismiss it.”

Do other actors welcome them? Murray nods his head in agreement. “I love getting notes.” Rigg concedes others aren’t so keen. “I’ve been in shows where people have been very ratty. Even if I said: ‘Take a couple of steps forward and you’ll be in the light.’”

Rigg’s support has allowed Murray to take both Boxman and his first show Big Sean, Mikey and Me to London and New York. He’s ambitious. He wants to make movies and has been to Los Angeles to meet people.

“I think it’s all about hustling,” he argues. “I started doing my own writing by accident because I wasn’t getting the work I wanted. But fortunately by making my own work I’ve been able to get other work. So one thing feeds the other. I think you’ve got to make it happen, so to speak.”

In fact, he says, he’s written a script called No Trees on Tiree. There’s a production company involved, a director on board. He’s hopeful. “And there’s a fantastic character that would be perfect for someone sat not far away from me,” he says, eyes on Rigg.

Rigg says she was never really ambitious. In her time in the industry it has changed beyond recognition, for good and ill. “In fact it’s odd to call it an industry. I can’t think of it as an industry at all. I can’t think of anything to do with the arts as an industry, although in Britain it generates more income than any other industry.”

Is that true? It is certainly not always recognised for its worth. “Absolutely not. And we always get wimps as our arts ministers.”

This is how our afternoon passes, a meandering conversation that finds its own way. To grease the wheels of our conversation I’ve brought some words with me. The idea is to get these two actors to riff on them.

For example, if I say the word regret, what springs to mind, Diana?

“I regret that I didn’t have more confidence when I was younger,” Rigg says immediately. That’s hard to believe. Rigg’s public persona has always been one of steely-eyed determination. She comes across as a woman who knows her own mind and is not afraid to let you know. (In the course of the afternoon she will time and again ask Murray questions herself. I’m not really needed.)

And yet, yes, she says, the younger Diana Rigg was lacking in self-belief. “I still got there but I was tortured. I’ve got little notes from Peter Hall when I was at the Royal Shakespeare Company on first night saying: ‘You’re almost there.’ The kind of note that makes your heart sink when you’re in your dressing room about to go onstage. ‘I’m almost there? I’m just about to go on stage for my first night.’"

Not that more confidence would have changed a thing, she says. “But I would have had less pain.”

Murray is hardly old enough for regrets, surely. Or maybe he is. “When I first came to London in 1998 I was quite a wild kid and maybe I wasn’t as focused as I could have been. But then I wouldn’t have the stories to tell that I have now.”

Hmm. Define that wildness, I say.

“I think he wants the juicy bits,” Rigg tells him.

“I grew up in the binge generation,” he says, “and in Scotland you have a healthy appetite for everything that's going at a young age. And when I came to London and was making money for the first time it was even more plentiful. I maybe overstayed my welcome with that. You live and learn. I had a good time. But I’m really focused and driven now.”

He’s based in London, but Scotland is a constant in life and work. Does he still recognise the Stockbridge he grew up in? “It’s very different now to what it was then. There were a lot more families then. There’s a lot more money now and it’s a little bit more faceless. A lot of the characters have gone. But I think that happens everywhere, doesn’t it? Gentrification. But it was always a beautiful part of town to grow up in.”

Rigg’s life in Scotland in the 1980s saw her, a middle-class girl from Doncaster, take on the life of the laird’s wife. “Fishing, shooting. Half your readers are going to tut at that. I don’t shoot, but I had dogs.”

She also loved her time as chancellor of Stirling University and director of the MacRobert Centre. Scotland, she says, gave her so much. “It gave me a husband I was so happy with for years and years and years.”

What’s her definition of love today? “Generosity, laughter, joy, individuality.”

Has that definition changed over the years? “Oh love when I was 14 was Gregory Peck. Nothing else. Love incarnate. I got to meet him many, many moons later. By that time I was over it but he was beautiful and lovely.”

Time passes. We grow older. “Age has never bothered me,” says Murray. There’s a 40-year-old talking, I almost say.

“Growing up, I’ve lost a few of my friends. They were quite young when they passed away and that just made me realise you’ve got to make the most of this.”

Do you feel like a grown-up now? “Never,” Rigg says. “You must never be an adult.” What? Not even when you become a parent? “When I became a mother I asked myself all sorts of questions. What did I believe in? What was I going to pass on knowingly? What was I going to pass on unconsciously? And in a sense you do at that stage define yourself a little bit more than possibly you did before.”

What was the one thing you told yourself I’m not going to pass on? “I was never going to send my daughter to look for my spectacles. I spent my life looking for my mother’s spectacles."

She pauses, thinks. “What was I never going to do? I would give her as much confidence as I possibly could, tell her she was beautiful as often as possible. Send her out into the world strong. Not aggressive, I hasten to add. Strong.”

Like Rigg herself, you might say. Diana, is age just a number? Does it matter? “It matters hugely. You can’t walk away from it. You have to accept the age you are. Old age is not for sissies.

“Nobody talks about the pain. Nobody talks about the decrepitude. But the most important thing is don’t lose yourself in your age. Be curious throughout your life. Keep learning. I learned French when I was 60.”

“That’s brilliant,” Murray says.

“The French wasn’t.”

Time for another glass of prosecco.

The Club runs at the Gilded Balloon Teviot, August 3-29.