Brandy. Arthur Cook reckons it's the elixir of life.
A couple of nips before bed every night had helped him reach the age of 100 at the weekend, he said.
"Oh, I like that - I like me brandy. It's purely medicinal, of course.''
If you can have an "ordinary life'' - that is, sleep well, work hard and eat healthy - you can have a long, healthy life, he said.
That's where the brandy comes in.
It helps him sleep well.
Mr Cook said he had had a relatively uneventful and healthy life on the whole.
The only time he felt his life might be cut short was during World War II when he was a member of the New Zealand Divisional Cavalry in Egypt.
He was wounded by shrapnel and received serious arm injuries.
But he recovered, and at the end of the war, returned to Dunedin, working as a tinsmith at the Hillside railway engineering workshops until his retirement.
With his failing vision and hearing, Mr Cook never thought he would make it to 100, but now
he was wondering what all the fuss was about.
"I feel great. Now that I've made it, I feel like I could go another 100,'' he said with a chuckle.
It was a revelation that buoyed family members during his birthday celebrations at the Distinction Hotel in Dunedin on Saturday.
The event was made even more special when he was presented with life membership of the Dunedin RSA.
Club president Lox Kellas said Mr Cook had been a member of the club for 66 years.
Mr Cook's wife Alma died about 10 years ago, but he continued to live in the family home until 2012.
He now lives at the Little Sisters of the Poor in Brockville, where he loves to talk about anything rugby-related, to anyone who will listen.