Luc Besson is an interesting film-maker, part visionary, part pulpy stylist. He has undeniable talent and visual flair, but far too often wastes this on trashy and juvenile comic book films, with a teenager’s preoccupations rather than a focus on story and character. One of the few exceptions to this is Leon, a film that marries his vibrancy with a heartfelt story.

Leon (Jean Reno) is a professional hitman working in New York, a dedicated professional with the stunted emotional maturity of a young teenager. One day the family of his next door neighbour is ruthlessly slaughtered by demented, drug-dealing cop Norman Stansfield (Gary Oldman), leaving only precocious 12-year Mathilda (Natalie Portman) alive. Despite his concerns about involving himself in the world, Leon takes Mathilda in – and these two outcasts develop a deep emotional bond, part mentor-pupil, part father-daughter, part celibately romantic.

In many ways, Leon should be an uncomfortable viewing experience. It’s a film that explores the growing emotional and sexual awakening of two characters, one of whom is a 12 year old girl, the other a hitman in his 40s. In fact it’s hard to imagine it even being made today by a Hollywood studio (it was controversial enough at the time). However, it works because the characters are so skilfully established. The 12 year old is precociously mature emotionally and sexually for her age, the man is so emotionally stunted and childlike in his outlook on the world he effectively feels like a 14 year old. The sexual interest is all from the girl, and is constantly batted gently aside (with a confused lack of understanding) by an adult who doesn’t understand the adult world and its feelings. As such, the film manages to side-step the creep factor and turn itself into a sort of touching fable.

It further works because our two leads give such terrific performances. Jean Reno perfectly understands Leon’s childish appreciation of the world, his touching faith in other people (his father-figure Tony is clearly swindling him), his simple delight in things (his wide-eyed appreciation of Singin’ in the Rain is very endearing). He’s naïve and has a child’s lack of understanding of violence and its impact. He’s focused so tightly on his narrow world, he’s clearly never developed any real emotional understanding of the wider world. Reno creates a character who is a seasoned killer who feels like a under developed teenager – emotionally and sexually he’s pretty close to being a 12 year old himself. His interest in Mathilda is rooted more in an elder brother/sister relationship. You get the feeling sex has never even really entered his mental equation. It’s a masterful performance, effortlessly cool but also stirringly real, sweet, vulnerable.

Equally brilliant is Natalie Portman’s enthralling performance as Mathilda. She creates a character who is sexually daring, seemingly far more adult and savvy than Leon in many ways, but is still recognisably a vulnerable child. She’s spiky and defiant, but this hides a deep rooted sensitivity and a desperation for love and affection. Her continued expression of sexual interest in Leon is as much rooted in a desire to feel part of a genuine caring family unit as it is some desire to initiate sexual contact. Her performance is perfectly nuanced and searingly real. Portman also feels both simultaneously adult and childish, so she never feels as out of place.