Kiwi director Gaylene Preston says the debut of her latest documentary "couldn't have been better", with the audience leaping to their feet to applaud the film at its conclusion.

My Year With Helen, which followed former New Zealand Prime Minister Helen Clark as she unsuccessfully campaigned for the role UN Secretary-General, had its world premiere at the Sydney Film Festival last weekend.

Preston, who had finished editing the film only days before Saturday's screening, says she was delighted with the response from the packed State Theatre.

"When you have your first screening, you don't know how it is going to work with an audience. This was amazing. People laughed quite a lot at things we didn't think would get a laugh and they started clapping at certain points. 

Read the interview in full here.