He was born in Australia on a Black Friday in 1946. Smith would be educated at a Seventh Day Adventist primary school - one of his first reports read "I am of the opinion Leighton can do better" - and he would briefly attend university.
He worked for a period as a taxi driver in Sydney. His first radio show was 30 minutes as a "junior disco jockery" on Sydney's SCH in 1962; he was 15. Smith first moved to New Zealand for a one-year stint with 2ZB in Wellington in 1980, but stayed for five. Lindsay Yeo, then "king" of Wellington radio dedicated the Mac David song Oh Lord, It's Hard To Be Humble to Smith when Smith's ratings surpassed his own.
After a brief stint on a radio in Adelaide, Smith was back in Auckland in 1985 at 1ZB, soon renamed Newstalk ZB. He has been there ever since, following Paul Holmes' breakfast show for many years. He was diagnosed with prostate cancer in 2002, three years after Holmes. Smith's father died of colon cancer on New Year's Day 1997.
Smith built a Tuscan-style villa and vineyard in Clevedon in the late 1990s, which he dubbed Il Monticello, the same name as the home of Thomas Jefferson, the third president of the United States. Smith has been married four times. Singer-songwriter Dave Dobbyn said recently he found God after being interviewed by Smith on his short-lived Sky TV show.
Smith was named Best Talkback Host of 2013 at the New Zealand Radio Awards. He publishes his memoir, Beyond The Microphone, (HarperCollins $39.99) on November 1.