Diana Rigg fairly bounced out of rehearsals looking like a born-again teenager in her lumberjack jerkin, jeans and sneakers and hit the street with a grin which announced that here was a lady without a care in the world. She was, on this occasion, still acting. Barely seconds later, she was raking a hand through her cropped hair and reaching for a cigarette before I had got the car into second gear as we drove to lunch and, just briefly, the unbreachable and imposing confidence which she normally radiates seemed to teeter.
Ms Rigg, as the gossip columns have documented, as a "situation" at home centered on the activities of her allegedly errant husband, Archie Stirling, and it is said divorce lawyers have been consulted. "Mention that and you're dogmeat," I had been advised in advance.
She also has a new play on her hands, with an emphasis on the new. For the first time in 14 years, this pedigree actress, who can equally command the classics, West End musicals or high-definition TV series, has opted for a contemporary play and is heading for her debut at the Royal Court.
As this was only the second week of rehearsal and she had spent the morning discussing how the still evolving piece should end, her uncertainty about how to describe it was allowable. I suggested this was where the going got tough.
"But that's the joy of it," she belted back. "For one thing, it erodes that stupid cliche that actors and actresses are mere mouthpieces. I am working with a playwright who is generous about what what the actors have to offer. It is wonderfully invigorating to be involved at the ground floor in a piece of collaborative theatre, which is what this is."
The play is the latest from Howard Brenton, called Berlin Bertie. Set in 1990, after the fall of the Wall, but with many a flashback, it follows Miss Rigg's character as a psychiatrist married to a Lutheran pastor, returning from Berlin to London pursued by a member of the Stasi secret police. "She is pursued for various reasons..." said Ms Rigg, dictating the dpts to avoid undue revelation.
Opening in Sloane Square on 14 April, the play is the latest piece in a highly industrious period for the actress. Since her award-winning performance in the Mother Love TV serial, she was memorably heroic as Cleopatra in Dryden's All For Love at the Almeida, led a revue of latter-day Sondheim songs called Putting It Together, and went to America for a TV film which put the ex-Emma Peel and former Bond heroine back among the spies.
"Mother Love did quite well in the States because the Americans lurve those monstrous women. The TV film was a very bright idea. I played the sort of M figure. The script said it was a rumpled man of about 50 but instead they had a rumpled woman of about 50. I enjoyed sitting behind the desk sending the spies off and barking out orders."
The Sondheim show, directed by Julia McKenzie, was staged at Oxford's try-out theatre, The Old Fire Station, and looked a West End certainty under Cameron Mackintosh's guidance but has since been put on ice.
Rigg and McKenzie were the centrepiece of Sondheim's Follies, but Ms Rigg said of their latest collaboration: "We had a wonderful last night but I think we all agreed the show needed more work. Getting the team back together again now might be hard.
"I have no musical training so the rest of the cast were always 250 yards ahead of me. But Steve has said he wants a dramatic input as well as musical. He told me it does not matter so much what sort of sound you make, it's how you interpret the song."
After the Almeida season, she and the company took All For Love to a Spanish theatre festival. "We were in a jewel of an Elizabethan theatre with bats swooping around but I had to climb 125ft of stairs four times a night. By the time we finished I worked out I'd climbed Ben Nevis. It went well at first but I'm afraid by the end we were playing to the caretaker and his family."
Now she has embraced new writing for the first time since she led Tom Stoppard's Night and Day. Why the gap? "When you have been around a very long time, as I have, they don't think of you for new plays. They only remember you for classics and revivals. The pigeon hole is imposed on you, it certainly does not come from yourself, and whenever the opportunity presents itself I like to blow the pigeon hole apart.
"I have actually played the Royal Court once, but only for a charity night. I shared a dressing room with Dame Peg, Diana Dors and Sheila Hancock. It's a really nice theatre and I like it. Why? It's very near home."
"Home. So how are things at home, Diana? Will the "situation" be resolved? A steely pause and she leaned forward: "Listen, mate, I've made a rule not to talk about any of that and I'm not going to break it, not even for you."
I moved on to courage in the face of adversity and she quickly steered the conservation to safer waters. "Courage is what theatre is all about. Life could be very cosy doing dressy revivals but it would be so boring. Theatre is all about fear, taking on fear and then dealing with it. I hope to spend the rest of my life in the front line of that fear."
That future looks to have little to do with the big companies. "They trundle, don't they. There is something inexorable about them. They have weeks and weeks of rehearsal, they get there, they do wonderful work but it hardly seems to have anything to do with theatre anymore. The best sort of theatre is flying by the seat of your pants."
For all her success on stage and TV, a consistent film career has eluded her. "You have to be realistic in this business and say there are others who got there first.
"I love going to the movies but when it comes to making them there is such an imbalance in the power structure. It's so top heavy. I might get a little tetchy. But a small independent film with a tiny technical crew and a committed producer - that would be rather nice."
She has noticed her new play's first preview falls on 9 April, election night. "I suppose the audience will consist of the author and the director."
Ms Rigg will definitely not be lending her public support to any party. "I think that is a really tacky trick. It demeans us as actors. What Glenda is doing is a completely different kettle of fish but just to climb on the bandwagon... You might as well be endorsing Fairy Liquid. Come on, darlings, can't you see you are being used?"