“My instinct was that it was best to leave a good piece of work alone,” says the woman behind The Virgin Queen and Small Island.
As the years passed, however, she found herself starting to think about it again.
“The whole premise of The Politician’s Wife was to use marriage as a kind of prism through which to look at contemporary political life,” says Milne of the original drama starring Juliet Stevenson as the wife of a politician whose life is thrown into disarray when she discovers he’s been having an affair with a former prostitute.
“At the time there was a lot of talk about family values. John Major had launched the Back to Basics campaign the year before, and so on. I began to think that if that template had worked then, perhaps a similar one could work now.”
But this time Milne, 65, wanted to reverse the story. “I wanted to explore the way men feel about their wives becoming more successful than them - that’s an interesting dynamic to set against the power games in Whitehall,” she says.
The couple at the centre of this story is Freya and Aiden Hoynes, played by Emily Watson and David Tennant.
At the start of the drama, Freya is the junior education minister and Aiden is attempting to run for the leadership.
“Initially, Freya seems like the dutiful wife who’s stepping back to allow her talented husband to take the crown,” says Milne.
But when the wave of support expected to carry Aiden to his coronation evaporates, Freya takes the opportunity to step out of his shadow and the resentment she’s felt over the years becomes clear.
Although attracted to a “cracking piece of writing”, Watson, 46, was also intrigued by the fact Freya is “quite an unusual female character”.
“She’s strong, faithful, sexual, political, ambitious, she’s a mother - all of that rolled into one,” says Watson, a two-time Oscar nominee who won a TV Bafta last year for her role alongside Dominic West in Appropriate Adult.
“You don’t end up being an MP or a cabinet minister without being unbelievably ambitious but the interesting thing about Freya is that she has an emotional intelligence to go with that.”
So where Aiden is a bit of a blunt instrument, Freya deals her cards in a more subtle way.
“Freya has a full orchestra of subtle, womanly ways at her disposal. And she knows how to use them,” says Watson, who adds she’d be “hopeless” as an MP.
“I have enough difficulty running my own life, let alone other people’s,” says the married mother of two.
Before filming began, Milne and the producers arranged for Watson and Tennant to meet people within the Westminster world to get a sense of “the politics with a small p”, says Watson.
“Some were very concerned about the power struggles, the back-biting world of Parliament. There was an impression that that was the be-all and end-all of politics.
“At the other end of the spectrum you got people who were really driven to do good and to improve people’s lives. I think both Freya and Aiden are an interesting mixture of those two things.”
Milne is the first to admit a drama about politics could potentially feel “a bit dry”, and for this reason chose the emotional engine of a marriage to drive the narrative.
“You have to engage the audience with the heart as well as the mind,” says Milne, who couldn’t be happier with her two leading actors.
“The most fantastic thing about them is that you would completely believe they are married,” she adds.
“As viewers, you should feel that there has always been an element of competition buried underneath this marriage.”
She doesn’t want to give too much away, but just as the sexual journey of the characters in The Politician’s Wife reflected the deterioration in their relationship, a similar device is used in this series.
“And, yes, it is quite shocking in places,” says Milne. “I think David’s performance is particularly brave, because Aiden’s a pretty irredeemable character.
“For an actor like David, who carries such a legacy of goodwill and love from an audience, it’s quite a brave thing to play.”
Like Watson, Tennant was immediately drawn to the prospect of brining Milne’s characters to life.
“She’s sort of television royalty, isn’t she?” says the former Doctor Who. “Aiden and Freya have to cope with this very different power structure within their relationship and there’s an aggressive streak in Aiden that emerges.
“But then again he’s a man who is pushed quite far. He’s had everything, and suddenly he has nothing. So I think it’s quite understandable that when he’s pushed into a corner, he comes out snarling and biting.”
Sporting what looks suspiciously like highlights in the drama, Tennant admits he had a certain amount of say in his character’s look.
“Watching a lot of the political faces we see regularly on the news, I was struck by how coiffed they are,” says Tennant, 42, who’s expecting a second baby with his wife Georgia Moffett.
“They often seem to go for a sort of Eighties soap star kind of look, but then you’re expected to look sleek and slick.”
Over the years he’s talked to many politicians about what their lives are like.
“What I found fascinating to imagine was the sheer stress of that life - the burden of it. But at the same time you could sense the buzz that people get out of it too.
“The high you get when you deliver something well in the House is like having a fantastic first night on stage and getting all the best reviews. It gives you that kind of a hit,” adds Tennant, whose depiction of Hamlet in 2008 was met with critical acclaim.
The actor admits he’s a sucker for a bit of political drama. “The West Wing is probably my favourite television series of all time.
“There are very few areas in life where the stakes are so high; where the power struggles influence not just the lives of the people involved, but also the lives of everyone they represent.”
So what does he think real MPs will make of the drama?
“I think they’ll love it,” he says. “It’s got all the hooks and surprises of a thriller, but with the depth and the texture of a quality character piece.”
The Politician’s Husband isn’t a totally damning portrait of politics - at least that wasn’t the reason Milne began writing it.
“I wanted to mirror how many people feel about the current political climate,” she says.
“I think in this country there’s a deep-rooted cynicism about the political system and writing the drama was an opportunity to refract those feelings of disappointment and to bed it into a story.”
So if you thought politics was boring, you’re in for a shock.