Invercargill Mayor Tim Shadbolt, right, sets out on the world's longest interview with CUE TV World Record Host Tom Conry.

Amid pontificating about the value of public speaking, Invercargill Mayor Tim Shadbolt today smashed the record for the world's longest television interview - and had to be cut off at the end.

Shadbolt started the attempt for the world's longest television interview at midday yesterday.

At 2pm today he hit his goal of 26 hours, after easily breaking the existing record at 30 seconds past midnight this morning.

A Guinness World Record official is on the Invercargill Cue TV set where the record was set.

At 12.01pm today Shadbolt set two other records - the world's longest broadcast on radio or television, set recently in Sydney, and New Zealand's longest-ever broadcast, held by fundraising television programme Telethon.

Cue TV general manager Sheree Carey said staff at the station had brought in mattresses to get some rest but interest had been so high they had only got one hour of sleep last night.

Viewers watched the live stream around the world, including the United States, Qatar, and Japan.

"I don't know why because they don't know Tim.''

The pair were fuelled on pineapple juice.

Shadbolt, a political activist-turned-politician and famed public speaker, could talk at length on any subject, Carey said.

Money raised from pledges went to St John Ambulance.

Tom Conroy, from Cue TV, conducted the interview.