"One day, I was shooting with Gerry (Butler), being in the scene with him, and also having to guide him and that was great - he was great - and then I had to do a speech I knew well, and I suddenly realised I'd given all my energy to someone else. I had to scramble."
Ralph Fiennes, a master of transformation on screen, has pulled off an impressive trick before my very eyes. In person, a few weeks ago at the Independent Film Awards, he appeared shy and uncertain, even with the Richard Harris award for contribution tucked under his arm.
Here, a month later, talking in less photographed fashion, he is direct, in control, and looks two decades younger to boot, with eyes of intimidating intensity, aided by a similarly blue shirt.
Ralph Fiennes is one of those rare beasts, a proper actor who just happens to be a film star, too. But even he was awed by the double task of directing and appearing in his Shakespearian epic Coriolanus, a very contemporary production of an ancient tale. Did his directorial debut ever threaten to overwhelm him?
"If I'd allowed it, there were times," he remembers, showing the courtesy of struggling for the right words, rather than speaking glibly off the tongue. "But I couldn't afford to think that. The more I was trying to make it happen, meeting people, asking them to distribute it, make it, design, it, I found myself very energized by wanting it to be made."
Fiennes has previously spoken about the relevance for a modern audience of Coriolanus - a warlord who is ousted by his city-folk because his heroic militarism is matched only by his pride and lack of love for them, reduced to plotting with his former arch-enemy Tullus Aufidius, played by Butler.
Fiennes has engineered a thoroughly modern reworking, aided by the same photographer who helped director Kathryn Bigelow to Oscar success with The Hurt Locker. But the project evidently got increasingly personal:
"I felt mentally tired, and physically exhausted, but I never felt that thing when I had to let go. If I ever felt the beginnings of that, I'd react against it very strongly, I'd think, what is the problem, what is it, address it?"
And the challenges didn't end once the cameras started rolling, it appears, with Fiennes desperate not to second-guess himself in the director's chair:
"I go in so anxious not to self-serve myself as an actor that I might err the other way. In the end, you just have to spin every plate.
"I had a wonderful woman Joan Washington, who was my dialect coach, but also gave me honest feedback on my performance. She would have an opinion, sometimes we would have debates, when she would say she didn't believe it, or it was too weak, or I was coming across as too theatrical..."
With a catalogue of onscreen work from Schindler's List and The Reader, to The Constant Gardener and The English Patient, not to mention years of Voldemorting against Harry Potter, Fiennes is probably better qualified than most directors to know when something's working, which, he reveals, is not always guaranteed even at these cinematic heights:
"I can be wrong, but there is a kind of area where even while you're doing it, you're on top of a wave, I've never surfed but I imagine it's something like that under you, carrying you. Other times, when you're fighting to get up there, it's all a bit harder. The ideal is to be in a state of concentration and relaxation, where the gods can give you their blessing, doesn't always happen."
It's happened often enough for Fiennes - Oscar-nominated twice, he remains circumspect about his latest BAFTA nod, for Outstanding Debut By British Writer, Director or Producer - "not very important, just great to be included", but can instantly cite his personal favourite role:
"I don't ever look back, once stuff is done, but I loved doing The Constant Gardener for some reason. I felt that I knew that man, Justin Quayle, and I loved what the film was, something good and new. And I loved the director, unpretentious in every way, open and honest."
Coriolanus is in UK cinemas now. Watch the trailer below: