Seeing Gandhi with crazy hair is even weirder than watching 64-year-old Sir Ben Kingsley snog 22-year-old Mary Kate Olsen. But fear not, the knighted actor hasn’t had some innovative hair treatment to unpolish his famously shiny snooker ball, he’s simply wearing a wonderful scarecrow-style wig in Jonathan Levine’s coming-of-age drama The Wackness.

Whereas it was easy to dismiss the brushed-back boot polish that he sported in Schindler’s List, this wig almost steals the show from right above him. The wiry angles the faux mop weaves seem impossible and are distracting as Kingsley plays a psychiatrist who swaps advice with a teenage dope dealer in return for some free narcotics.

So when he clasps my hand at a swanky London hotel, I’m glad to see the light is bouncing cinematically from his pate in the same familiar way it does in Gandhi, Sexy Beast and more recently, Elegy.

Once we’ve sat down and The Wackness star has courteously poured us both a still water, I can’t help but ask him about his new hairdresser. ‘I needed the wig to play Squires,’ he says. ‘If I were to draw a lightning sketch of the character . . .’ he begins before springing off at a tangent. ‘It’s hard to talk about acting and there is a lot of nonsense spoken about acting, but I think I’m becoming something of a portrait artist as an actor because the camera really is portrait, it’s not a great landscape painting, theatre is landscape.’

Just as I’m starting to wonder if he is being ironic about actors speaking nonsense about their craft and what this has to do with wigs, Sir Ben adds: ‘I sort of saw Squires with wires coming out of his head, as if the madness couldn’t be contained in his skull, that he had a halo of unruly hair around his head. I put that to Jonathan and he liked the idea. I couldn’t go to him as I was filming Elegy at the time I was preparing for The Wackness so he sent a make-up person over to design something for my head. When I came out of the trailer for the first time wearing a Hawaiian shirt he said, “There he is.” I was really touched that the silhouette I presented to him was close to his vision of Squires. I think it’s important to present a classic silhouette that you can really push into the audience’s memory, onto their retina or their perception. That is why I don’t like to change my clothes very much in a film. I have one or two outfits. Gandhi is one.’

I’m intrigued by his painting analogy and wonder what artist the actor most closely associates himself with. Is he a Picasso or a Pollock, like his wig? ‘I’m not brave enough to be a Picasso,’ he says. ‘He had this beautiful way of painting, like a child; there is something completely uninhibited about his work. So I don’t know who I am really.’

I baulk. There are many things you can say about his acting, but being inhibited is definitely not one of them. Let’s not forget this is the man that scared the living daylights out of Ray ‘The Daddy’ Winstone in Sexy Beast, makes a police officer cower like a child in House of Sand and Fog and played the imposing magistrate Porfiry in Joseph Sargent’s Crime and Punishment. I probe for more explanation. ‘Yes, I think I’m a little too locked in the detail,’ he says. ‘I’m a little too careful sometimes. If I were painting I’d be the one trying to mark completely accurate lines. I’m dead perfect on my dialogue. I rarely improvise unless there is a director who insists that he wants to run with it for another 15 seconds and asks if I can carry on. I don’t normally like improvising. It’s my theatre training. I like staying on target as it were. I like to visualise the target as a stream of words or movements. Within that, I’d like to be just a little bit more carefree. With comedy, it’s a great opportunity to be carefree.’

Some would argue that by sending up his Gandhi performance in the appalling The Love Guru, he wasn’t being carefree, but careless. It seems the actor may feel the same way, for when I bring up the Mike Myers film, he answers with a question. ‘Have you seen The Sopranos? That is self-satire.’

It’s funny to hear Sir Ben talk about self-satire as his sense of self-importance and insistence on being called ‘Sir’ were called into question by Lord Puttnam in 2006 when the poster for Lucky Number Slevin billed him as Sir Ben Kingsley. His attitude is a bit pompous, but so is the honours system that awards knighthoods to actors mid-career, so if he wants to be pedantic about it, then that’s the way the cookie crumbles.

Meeting him face to face, I am happy to call him by his title, more so because he’s a boy that’s done good. Born in Yorkshire, his father a Kenyan-born Indian physician and his mother a fashion model with a Jewish European background, Sir Ben, a promising singer and guitarist, made his stage debut in 1966 and was soon snapped up by the Royal Shakespeare Company. He also appeared in a handful of episodes of Coronation Street. He forged a fierce reputation as a Shakespearean actor before moving into cinema. Then, in 1982, he played Gandhi and became the first actor of Indian descent to win the Best Actor Oscar. I was only seven at the time but I can still remember the sheer glee on my Pakistani father’s face when he won.

Recently the actor seems to have been recast as a ladies’ man. As well as playing Famke Janssen’s husband and snogging Mary-Kate Olsen in The Wackness, he wooed Penelope Cruz in Elegy, while Tea Leoni was his belle in You Kill Me. He also reminds me with a gleeful grin that he had some rather erotic scenes with Annette Bening in Mrs Harris. Life seems to be mirroring art as the actor recently got married for the fourth time to 32-year-old actress Daniela Lavenda. It’s with another glint in his eye that he tells me that his new wife is the best judge of whether he’s got sexier over time. It’s true, he does become more carefree when doing comedy. A bit more of that and his dream Picasso inspired performance may come sooner than he thinks.

The Wackness is on general release from Fri 29 Aug, see next issue for review; Elegy and The Love Guru are out now.