That crazy little thing called love complicates a seemingly perfect relationship based on sex in Ivan Reitman’s contemporary comedy of social mores.

As the title suggests, No Strings Attached centres on a pair of 20-something professionals who don’t have time in their busy schedules for an inconvenience such as commitment.

And so they agree to be friends with benefits, calling and texting each other for physical gratification with the understanding that they don’t have to worry about the awkwardness of post-coital conversation or sneaking out before breakfast.

As Harry and Sally discovered, when they met more than 20 years ago in Rob Reiner’s iconic romantic comedy, men and women cannot be friends without emotions getting in the way.

Thus screenwriter Elizabeth Meriwether gradually shows her protagonists the errors of their lustful ways and sets up the possibility of a happy ever after using that age-old plot device: A family wedding.

In the wrong hands, No Strings Attached would be saccharine nonsense.

Thankfully, this film is blessed with director Ivan Reitman and well-judged performances from Natalie Portman and Ashton Kutcher, who generate smouldering on-screen chemistry.

Adam (Ashton Kutcher), whose father Alvin (Kevin Kline) is a famous actor, works as a lowly TV producer on a show that is cynically jumping on the High School Musical bandwagon.

‘It’s about high schoolers, who sing and dance and blog,’ he reveals dryly.

After disastrous previous encounters, Adam stumbles back into the life of medical student Emma (Natalie Portman), who once told him, ‘People aren’t meant to be together’.

They agree that there would be no harm in no-strings-attached sex as and when the need arises.

Adam’s friends Eli (Jake M Johnson) and Wallace (Chris ‘Ludacris’ Bridges) are envious that their buddy has found the perfect woman.

Meanwhile, Emma’s housemates – including fellow medical student Patrice (Greta Gerwig) – diagnose imminent heartbreak.

No Strings Attached is the first touchingly sweet and uproariously funny Hollywood rom-com of the year, anchored by winning performances from Kutcher and Portman, the latter bound for the Oscar podium for yesteryear’s Black Swan.

Their comic timing is impeccable but more crucially, they both allow the characters to wear their hearts on their sleeves, shedding tears as they face the possibility of losing each other forever.

Kline relishes a larger than life supporting role and indie favourite Gerwig nabs the best line of the entire film relating to her period.

This leads to one of the film’s best scenes when Adam soothes Emma during that fractious time of the month with cupcakes and a CD of fitting songs such as Bleeding Love by Leona Lewis and Sunday, Bloody Sunday by U2.

‘Adam, did you make a period mix?’ grins Emma sweetly.

Beleaguered husbands and boyfriends – take note.

• Release Date: Friday 25 February 2011
• Certificate: 15
• Runtime: 108mins