Diane Keaton had been an icon since before I was even born; who was I to direct her? To fill her head with my dialogue? To give her a note, suggesting: “It might be even funnier if you tried …”?

And yet, as she towered over me in sky-high Gucci platform booties, she never made me feel even one inch less tall as I guided her through what would wind up being her final film.

What you see on screen is exactly who she is – though you may be surprised to learn she had a mouth like a sailor

While many will remember her for her brilliant performances, for the way her laugh instantly transformed a room when she entered or the way she added levity to even the most arduous of night shoots, I will remember her most for what she taught me about being a woman. Diane didn’t merely exist in the world, she shaped it around her, carving a space for herself to be unapologetically Diane. She knew who she was and what she needed to be at her best – such as a second hotel room so that on weekends she had a space to design her next art book. She loved to work and rarely took a day off. But perhaps most importantly, she possessed an envious level of confidence without ever crossing that tenuous line into arrogance.

Summer Camp cast and crew: Alfre Woodard, Kathy Bates, Diane Keaton, Dennis Haysbert, Castille Landon and Eugene Levy. Photograph: Courtesy: Castille Landon

What you see on screen is exactly who she is – although you might be surprised to learn she had a mouth like a sailor. Her quirkiness wasn’t curated, but born of her unfiltered, naturally incandescent self. In an era in which authenticity has become yet another buzzword, when women are pushed towards homogenisation, Diane stood firmly outside the algorithm. She had no interest in following trends, and I don’t even think it was her intention to set them. And the idea of dressing or behaving in a certain way, so as to appeal to a man? Laughable.

She had no interest in following trends. I don’t even think it was her intention to set them

While I don’t know whether she considered the male gaze earlier in her life, I can unequivocally say it wasn’t a factor that affected her in the time that I knew her. But, of course, this ethos of individuality and freedom was magnetic, on-screen and off. She wouldn’t hesitate to banter with any crew member capable of matching her quick wit, which often led to handsome, young cameramen dissolving into puddles at her feet as she sashayed away at wrap, seemingly unaware of the effect she had on people, of the power she contained.

She truly created her own reality and that’s where she lived: untouched by so many of the menial concerns that consume we mere mortals. In this way, she maintained a certain childlike innocence – a youthful vigour and love of life, approaching each interaction, whether it be with her co-stars or an intern on set, without an ounce of inhibition. She wasn’t fearless, but she faced her fears head-on, with fierceness and determination. Nothing proved that better than when, after about an hour of back-and-forth, as the sun dipped below the horizon, she agreed (at 77!) to jump off a zip-line platform for the final shot of our film.

No pretence … Diane Keaton, Kathy Bates andAlfre Woodard in Summer Camp. Photograph: Entertainment Pictures/Alamy

It only occurs to me now that, in a career spanning decades, littered with awards and box office hits, it was with me that she spent her last day on a film set. We shot late into the night, going slightly past our agreed time. She was exhausted, I could tell – six weeks trekking the mountains of Asheville, North Carolina, shooting in river rapids, doing her own stunts and pratfalls and a daylong food fight would be a lot on any actor. Add to it that she had spent days off flying in and out of town to do press for another movie. But she kept showing up, for each and every take, giving every ounce of herself. And make no mistake, it was herself – unlike actors who wanted to be called by their character’s name, she insisted on being spoken to as Diane. No pretence, no beating around the bush or back channelling through her assistant, she wanted to be addressed directly, as herself. She was, and will for ever be, Diane.