Scott Coleman was only five years old when he first laid eyes on the Crown Jewels.
In fact, they were only replicas, on display in the Queen Victoria Building in Sydney, but Mr Coleman was hooked for life.
"I would sort of stand mesmerised by their beauty," he said. "They're nothing to the originals, but they really sparked an interest for me."
Although he has never visited England - or even left Australia - the 23-year-old has since become an expert on the royal family, with a particular interest in the Queen's jewellery collection.
"The Queen has multitudes of really fabulous jewels, and I've always been interested in them because they've been a silent witness to great historic events, like royal weddings and coronations and revolutions," he said.
"Many of them have gone through wars and have fantastic stories attached to specific diamonds and specific pieces that the Queen continues to wear today, so I've always been interested in that."
He said he had built up his knowledge of royal history mostly through books and exhibitions, and was disappointed not to be able to fly to England in 2011 for the royal wedding due to health problems.
He did, however, manage to score an invite to Government House for the Queen's visit in 2011, and had the opportunity to "say hello" to the monarch.
He will be giving a lecture on Sunday at the National Portrait Gallery, focusing on the recent royal portrait by the Sydney artist, Ralph Heimans, in which the Queen is wearing a particularly magnificent diamond necklace.
Mr Coleman will be explaining how the diamonds once belonged to Queen Victoria who, finding herself without a significant collection of jewellery upon being crowned Queen of England, set about rectifying the situation.
"She had a lot of useless bits and pieces that she couldn't wear, like a great jewelled sword and huge big badges of various orders of the garter and thistle," he said.
"She had all these big, big diamonds prised out of old useless pieces and had them made into a beautiful necklace. That necklace is known now as Queen Victoria's coronation necklace, although it wasn't made until the 1850s, many years after her own coronation. It has been worn by every queen, consort and of course the monarch, ever since."
He said it was difficult to imagine the size and splendour of the jewels in the portrait, which together comprise more than 100 carats.
"What I'll be talking about in detail is the way the jewels have been adapted to be worn by successive queens to suit their own tastes, and changing fashions of the day."