The promotional poster for the film Separation City consists of a just-married couple in a passionate embrace and a glistening pin hovering dangerously close to a heart-shaped balloon. The tagline reads: “It only takes one prick.”

However, there isn't just one prick in Separation City, there's a whole cluster of them. Shy Simon who cheats on his unsuspecting wife Pam, dinosaur politician Archie whose eyes perpetually rest on the décolletage of a much-younger female colleague, and love-rat artist Klaus, are just a few that come to mind.

When New Zealand political commentator and satirist Tom Scott first conceived the plot for Separation City in 1982 a number of film industry women were so outraged by the behaviour of film’s male characters that he thought it unlikely the movie would ever get made. Twenty-six years later it has, with surprisingly few changes to the original script.

“When I first wrote it [the script] the response from women was that biology’s not destiny. They were appalled and disgusted, but I haven’t changed those elements in the film. I showed it to my mother back then and she liked it, and my 20-something nieces don’t find it vulgar at all, that’s how they think women and men in long term relationships really are,” says Scott, who ironically won an award for “Woman of the Year or Feminist of the Year or something like that” in the ‘70s for choosing to be a stay-at-home dad.

Set in Wellington, the film revolves around the crumbling relationship of 30-something couple Simon and Pam, played by Joel Edgerton and Danielle Cormack. Simon longs for the intimacy he shared with his wife when they were first married, a period of time when he thought he was the luckiest man in the world. But rather than trying to fix the relationship he pursues an affair with a beautiful cellist named Katrien (Rhona Mitra) who is already married and, to add insult to injury, a friend of his wife’s.

For Separation City’s 40-year-old director Paul Middleditch the script struck a chord: “I’m married with a five-year-old daughter and a six-month-old son and I’m in a situation where I’m the breadwinner and while my wife has her own professional interests, for the moment she’s a mum,” her says. “So the dynamic of the relationship between the leading couple in the movie is very, very close to my life.”

“I think a lot of the questions that were raised about dealing with romantic and sexual issues, and dealing with children, were really close to home for a lot of people who contributed to making this film.”

While Middleditch could relate to certain elements of the script, he felt the need to slightly tweak the way the relationships were portrayed by the actors in order to bring the film into the 21st century.

“[The script] dealt with some quite confronting issues and I thought it was really brave and bold. But the characters in the film are my age, not Tom’s (who’s 20 or so years older than I am), so I thought it was important to contemporise some of the themes,” he says.

“The actors did a really good job of ensuring their characters rang true to what we experience today as a different generation of married couples to the ones Tom concocted in the ‘80s. These days, there’s a lot more out in the open. Men in many ways are now more aware of equality and relationships. I wanted to make sure that that was obvious in the film.”

Middleditch felt that the character of Pam needed to be stronger and more culpable for the breakdown of her marriage, to create a sense of “it takes two to tango” in the movie.

While Danielle Cormack asserts that her personality is nothing like her character's (who she describes as “nagging”), the actress does understand why Pam's marriage ended up faltering.

“They’ve reached the duldroms of a very domestic life,” she says. “I understand Simon’s actions and don’t think that he made a huge mistake. I think in many cases human biology wins over, and that there’s only a certain period when two humans share chemistry. What the film showed was how to get that bond back, you have to take a step back and look at what you’ve got.”

Scott, who is also the film's producer, was particularly impressed with Cormack’s portrayal of Pam: “Danielle, or Pam, has such a luminous quality that you want to shake Simon and say, ‘Why would you have an affair?’”

Asked how she achieved said luminosity, Cormack is refreshingly blunt: “I just turned up. It really wasn’t that hard. I didn’t think, ‘Oh I’m going to be luminous in this scene and steely in the next.’ Those are Tom’s descriptions really. I just wanted Pam to be a balanced and real character, which meant that I was warm as well as tough – this may have worked against feeling sorry for Simon but that balanced need to be achieved.”

Scott has grand visions for the film and hopes it will do for New Zealand, and Wellington in particular, what Woody Allen's films have done for New York. “I wanted to show New Zealanders in successful jobs, leading busy lives and living in beautiful homes,” he says.

The luscious landscape shots that New Zealand films are renowned for are few and far between in Separation City. But inevitably, Wellington’s famous wind is featured. “You’ve probably got some of the strongest crews in Wellington - just to be able to hold the equipment,” jokes Middleditch.

Separation City is released on August 6, 2009.