Bill English reveals how he forgot his shoes before the Joseph Parker fight

The soon-to-be Prime Minister may need a bit of help getting organised.

Bill English was caught traipsing around The Warehouse on Saturday night after he forgot shoes to wear to the Joseph Park v Andy Ruiz Jr fight.

As explanation for the pre-event hiccup, English said he had had a busy day watching his son's first amateur kickboxing fight. He suddenly realised he didn't have any black shoes for the black tie event he was about to go to. So he stopped by The Warehouse to buy some.

"I was stopped by a few people who said they didn't expect to see the next Prime Minister wondering around on Saturday night in The Warehouse. But there you go."

This afternoon English will become New Zealand's 39th Prime Minister.

The job will officially become vacant after John Key's formal resignation at Government House following lunch.

English will be sworn in as the leader of the National Party after a caucus vote this morning, after which he and Paula Bennett will be installed as Prime Minister and Deputy Prime Minister.

In an interview this afternoon with Jamie Mackay on Newstalk ZB English described how his political upbringing shaped him.

"My parents were forthright in their views and thought it was important that we were raised to know what was right.

"Discussion was occasional and not always welcome.

"It was a fantastic environment to be brought up in."

Mackay called his mum and dad "political animals".