NEW YORK — Richard E. Grant has published wickedly funny diaries about the ups and downs of his life as an actor, but he had to tread more gently when it came to telling the story of his childhood in Swaziland. “Wah-Wah,” his directorial debut, chronicles his mother’s adulterous affair, his father’s descent into alcoholism and subsequent marriage to a high-spirited American “airline hostess,” who sticks out like a sore thumb among the stuffy colonials clinging to the last gasp of the British Empire.

“It’s entirely autobiographical,” Grant says by telephone from London. “Everything that happened, happened to me. The process of writing it was painful and joyful by turns.”

The movie, which opens Friday in New York and Los Angeles, begins with Grant’s character, 11-year-old Ralph Compton, inadvertently witnessing his mother en flagrante with his father’s best friend. When the beautiful, icy Lauren Compton (Miranda Richardson) runs off with her lover, her husband Harry Compton (Gabriel Byrne) seeks comfort in the bottle. Byrne is by turns charming, brooding and explosive. He bullies his son and even attempts to shoot him during one drunken rage.

“I knew my father’s alcoholism, which was so hidden away, was a family secret we had to keep,” Grant says. “He was by day such a charming, good guy. Only when he was overtaken by drink and his unrequited love for my mother did he become a demon.”

The second Mrs. Compton, played by Emily Watson, is an eccentric feminist, given to wearing wildly patterned caftans and colorful turbans. She has no patience with the snooty, hypocritical officers’ wives who cling to their traditions and petty biases, and ridicules their gossipy chitchat as sounding like “wah-wah.”

“I loved Ruby,” Watson says. “She was really good fun to play. She’s very redemptive, and liberated. Richard’s father remarried quite suddenly, but his real stepmother was Jewish South African. People wouldn’t understand how ostracized she would have been in British-ruled Swaziland. Making her an American made her an outsider.”

Grant’s first screen role came in 1986 when he played a drunk, out-of-work actor living in a house bereft of heat, in “Withnail & I,” which became a cult classic. He also appeared in Martin Scorcese’s “The Age of Innocence.”

This story first appeared in the May 11, 2006 issue of WWD. Subscribe Today.

But Grant actually has been writing longer than he’s been acting. He said he kept a diary as a boy and has published a journal about the making of the film, called “The Wah-Wah Diaries” (MacMillan). The book traces the process of bringing the film to fruition, from October 1999, when Grant began writing the script, to 2005, when he landed a U.K. distributor. The in-between was marked by endless frustrations.

Despite all of the hurdles, the film had one major positive result: Grant said he’s had a reconciliation with the mother who abandoned him 35 years ago. “The film provoked her to write to me after years of estrangement and tell me about what it was like to be a young, bored colonial wife,” he says. “Being attractive was the one weapon she had. She’s 74 now. I thought, ‘How could this person who has gray hair have been the Lauren Bacall of Swaziland?'”