IT is a measure of how grim conditions were while filming In Darkness, Agnieszka Holland's Oscar-nominated wartime drama, that she describes the rats as "actually pretty nice".

There was also the cold, the freezing water, and of course the darkness. When filming was finished some of the crew joked that leaving the sewer where the film is set was like departing a gulag.

Holland recounts all this with a laugh, as befits a filmmaker who has lived through some interesting times. Now 63, with a career that has gone from Soviet-era Poland and Czechoslovakia to directing The Wire for American TV, via Oscar nominations for Europa, Europa, Angry Harvest and In Darkness, Holland is a director more deserving than most of the prefix "legendary".

In Darkness, set in 1944, is the true story of a Lvov sewer worker who finds himself protecting a group of Jews who have fled underground to escape the Nazi atrocities. Holland, whose father's family died in the Warsaw ghetto, took a lot of persuading to do the film. She had immersed herself mentally in the war in Europa, Europa and Angry Harvest and knew how painful it was to spend time in that era, "in the reality of that horror, and how you pay for that with your body and soul".

What made her change her mind? "The stubbornness of the writer, handing me the script over and over again till I started to dream about it."

Filming in those conditions was terrible, she says. "Everything was difficult on this film. The only lovely thing was the actors were fantastic. It was very harsh on them as well so they needed real support."

Though the cold and gloom might be almost bearable, many actors would have baulked at the rats, trained and clean showbiz rodents though they were. Not Holland's cast. "I was afraid for the kids, that they would be scared but after one day they were playing with them."

In Darkness is unflinching when it comes to the horrors of surviving underground. It is equally clear-eyed about how life went on, including sex lives. Holland was determined not to shy away from that.

"I was angry at the way Jewish characters are presented in Holocaust movies, faceless and bodiless and victims. When I talked to the survivors, the people who went through this experience, everybody says it was a time when love, sexual love, any kind of closeness, was so vital and so present."

Born in Warsaw in 1948, Holland trained in Prague then worked in Poland. When martial law was declared in 1981 she was living in France and stayed there. It was a blessing to be able to continue her career elsewhere, but one she still has mixed feelings about.

"If martial law had not happened, if I had continued with my Polish movies, maybe I would be a better filmmaker today, who knows? It made me richer to work in different places, and more famous in some way, but I had to spend so much energy fighting and compromising and translating myself into different realities and languages. If that energy had gone into my craft it would be probably better, I don't know. I never regret things, what happens happens. I can't complain, I'm in a much better situation than most of my colleagues, and certainly most of the female filmmakers after the war."

The restrictions in Communist Poland were not as bad as in Czechoslovakia. She's been back in Prague recently to film a mini-series, Burning Bush, for HBO, and has been meeting some of her old film-school friends.

Despite the rules, overt and otherwise, she remembers the 1970s as being among the happiest periods in her career. "Some amount of oppression is actually quite positive I think. It gives you the subject, it gives your audiences the desire to communicate with you, but of course it has to be a limited amount of repression. If it goes further you just cannot work."

These days she is based in America, visits Poland frequently for family reasons, and has a house in France. Foreign films are more interesting than American movies at the moment, says Holland, but American TV has become the place for innovative writers and directors to work. She has directed episodes of The Wire, Cold Case, The Killing and Treme. "It's refreshing. Everything happens quickly, it's very intense and you get an immediate response."

The Wire has been a favourite. I tell her that I struggled with it till I found the subtitles button. She laughs. "I had to read it several times to understand exactly what they were talking about. After a while you understand the meaning of it." But it was "fantastic", she says, "so well written and well acted".

Among her remaining ambitions is to return to her roots with a small contemporary Polish film. Just one hitch: she doesn't have a script yet. Given this writer-director's track record of treating hurdles like matchsticks, that surely won't be long in arriving.

In Darkness opens in cinemas next Friday