The lustrous hair, the perfect skin and the eye sparkle all argue against the lady being very close to 67.
The Academy Award nominee also exudes the calm and gentle warmth of the comely wife characters she has played so convincingly in the likes of Patriot Games and Fatal Attraction.
However, all that sits incongruously with the realisation the rather chic lady is about to spend three weeks in the pressure cooker that is Edinburgh Fringe theatre, playing a real-life woman who's tougher than an audience of alcohol-denied critics.
Archer is set to play the lead in The Trial of Jane Fonda. Now, the world knows how Fonda became a Forces favourite after she played intergalactic sex kitten Barbarella - and then became vilified by ex-vets after she visited Vietnam in 1972, trashed the Nixon-Kissinger regime and was re-christened in the Republican press as Hanoi Jane.
But what we didn't know was that, in June 1988, Fonda met with 26 Vietnam vets in Waterbury Connecticut after the ex-soldiers protested during her filming of Stanley and Iris with Robert De Niro. Fonda and the vets took to a local hall to settle their differences over a tearful, traumatic, soul searching, heart-wrenching four hours. Emmy Award-winning writer Terry Jastrow reckoned this encounter offered huge dramatic potential, and he was right.
Why Archer as Fonda? Well, Jastrow is in fact Archer's husband but that does not mean she is wrong for the part. What matters is can she convince as the radical actress and offer a tougher edge than we've often seen on celluloid? Yes, Archer landed great reviews for her Mrs Robinson in the West End, but that's a world away from playing a real, live film legend.
Is the actress trepidatious about playing Fonda? "Why?" she quizzes, rather defensively, putting down her tea cup. Because Jane Fonda is a legend? "Yeah, well, because she is very much alive and very much in the public eye, yeah, it really is a challenge. But you just do the best you can and remember it's a great story and it's really well done. And I feel very strongly about the issues Fonda felt strongly about it."
Fonda had not been politicised until confined to bed in Paris after a difficult pregnancy when she began watching the wall-to-wall TV footage coming out of Vietnam. Inflamed by the indifference to human life displayed by Nixon-Kissinger she travelled to Vietnam, was photographed sitting on a North Vietnamese rocket launcher, and became "the most hated woman in America".
"These Forces guys had Barbarella on their locker doors and they couldn't handle the fact their sex idol was now an activist," says Archer. "It was too much for them."
Archer was never as radical as Fonda. But she shares her liberal sensibilities. Indeed, her life parallels that of Fonda in many ways. Her parents John Archer and Marjorie Lord were reactionary Hollywood actors. "My parents were Republican. My mother wasn't in any way involved in social issues but, because she worked a lot, my grandmother raised us and she always argued for integrity. During the Vietnam war, boys I knew were forced to go over and fight. One boy I knew died and my first boyfriend in college fought against the draft.
"Everyone, except in the southern states, protested against the war and there were coast-to-coast college protests. All this informed my thoughts on government policy. And don't forget, it all got so violent with the Kent State situation." (Archer was 22 when the Ohio National Guard shot dead four Honours student protesters, including a 19-year-old girl.)
Archer shares Fonda's mindset, but does she have the innate toughness that Fonda could call upon in real life and in films such as Cat Ballou? A hint of inner steel emerges when she's asked how she feels about putting her head above a parapet; Edinburgh will allow this political play to be filtered through the prism of social awareness and context. But what about the less liberal US?
"You know what," she says, her voice a little brittle. "The States can produce great critical art on the form of Coming Home or Born In the Fourth of July. And if you put fear out there and the press want to say this is fearful, then you can do that, but I don't agree with your premise at all.
"I think it's smart what we're doing. And I think theatre, going all the way back to Chekhov, has long put forward a notion the public wouldn't agree with."
She adds, on a roll: "In the UK and the States we have democracies that are responsive, respectful cultures."
"I'm not concerned about this play," she says in softer voice. "I know that it will be controversial, but if you produce a piece of art you want people to go see it."
Terry Jastrow reveals Hollywood has already shied away from the story, researched massively and written originally as a screenplay.
"Too much of a hot potato," he offers. So now it's a play to be showcased in Edinburgh which will hopefully travel to the West End, and then take the Frost-Nixon route onto film.
Jastrow points out The Trial of Jane Fonda is entirely balanced; had the Vietnam war been a 'declared' war many people think Fonda would have been tried for treason, and found guilty. "But now what we have is the trial of Jane Fonda in the court of public opinion."
Archer concurs: "This isn't a love letter to Jane Fonda by a long shot. The vets arguments are very persuasive, you hear their personal stories about loss of life and your heart goes out them."
Her tone certainly convinces you she can pull off perhaps the toughest performance of her life.
"When we workshopped this play before an audience I didn't know how they would react each night, but in playing Jane against the vets I felt I had to fight for me life. I loved it. I loved the emotional journey, being electrified."
She adds, smiling; "But will I be nervous on opening night? You bet. But that's all part of the journey too."
The Trial of Jane Fonda, Assembly Rooms, George Street, Edinburgh, July 30 - August 24.