When Oscar-nominated screenwriter David Seidler hits the red carpet at the Academy Awards next week, his Kiwi son will be watching with pride.

But Marc Seidler has revealed how he almost tried to talk his father out of writing The King's Speech, the film that has been nominated for 12 Oscars.

It was on one of their annual month-long father-and-son trips into the remote New Zealand bush that Marc first heard about the script, which tells how King George VI turned to a speech therapist to cure his stuttering.

"He told me the whole plot and I am sitting there going 'Dude, you're nuts, mate'," said Marc, a Piha-based news and current affairs editor.

"I thought 'that's just dumb, if I wanted to see stuttering I would just go and see Porky Pig - you know: 'Th-th-th-that's all folks'.

"No one is going to spend an hour an a half watching someone trying to go through their lines."

This week Marc spoke for the first time about his loving, yet fractious relationship with his script-writing father, who has won plaudits at the age of 73 after a career spanning more than 45 years.

"My old man has a sense of humour and he is very, very bright," he said. "He recently said to [Hollywood mogul] Harvey Weinstein, 'You know what, I thought I'd let you know that I never stuttered, I just made this all up'." (Seidler drew from his own painful battle with a speech impediment to write the film, which stars Colin Firth, Geoffrey Rush and Helena Bonham Carter).

Speaking from Los Angeles, David revealed he had kept a promise to the Queen Mother - who was married to George VI - not to write the movie while she was still alive because it would be too painful.

And he said that he felt right at home on his annual trips to see Marc and hang out in the New Zealand bush.

"We go to the Ureweras, we stay at my friend TJ's place. We get into it. We bond and we talk. It's good times. I really love the outdoors. That is my soul food. I come down once a year and feed my soul."

David met Marc's mother Huia during a trout-fishing trip when she was working as a waitress in Rotorua.

"When he split up with my mum he could have bailed and he never did," said Marc. "He always helped me out if I got stuck. I could always count on Pops."

Growing up between Rotorua and fashionable Malibu, in California, Marc says he never really fitted into either world and was bullied.

"It was an adventure going to live with my rich Pakeha dad - that's how I perceived it at the time but it wasn't because he was struggling you know," said Marc.

"Coming from Rotorua growing up with Maori as a kid then going over to live with my dad - because Mum and Dad would take turns looking after me - I would go over to America and say things like 'F***** honky bro' and 'Rich f****** honky dad'. I wanted to be in the Mongrel Mob."

David said he was aware Marc felt "displaced".

"He found himself really caught between two worlds which is a great shame."

But David said he was immensely proud of the person Marc had become, despite a difficult upbringing.

"I love him, absolutely. He is a very talented and intelligent chap - very bright, very sensitive but he sometimes hides it under a bushel."

After watching the film for the first time on Friday night, Marc said he walked out of the cinema "grinning from ear to ear".

"If I had a giggle-ometer for the audience I would've clocked it over. As I was watching it I thought, 'Oh my God this is my dad's story. This is him'."

Despite all the hype, David was talking down his chances of winning the gong for best original screenplay at the ceremony next Monday (NZ time).

"You never know about Mr Oscar. He is a very unpredictable chap. He can decide to go on dates with people you don't expect he's going to go on dates with."

Marc said he had hoped to emulate his father in a career of writing and directing, but had been beaten by "a lack of self-confidence".

And David is full of encouragement for him. He said: "When I was his age in the early forties I was broke and going nowhere so there is hope."