There’s a wonderful photograph of 15-year-old Ian Thorpe at the World Championships in Perth in 1998. Standing quietly, readying himself to compete in the 400-metre freestyle final – which would see him become the youngest ever individual male world champion – West Australian photographer Brett Canet-Gibson trained his camera on the contemplative, young swimmer and took a stunning shot.

Rachel_Griffiths Rachel Griffiths, 2002 by Karin Catt. Collection: National Portrait Gallery.

That image of Thorpe is one of 68 photographic portraits from the collection of the National Portrait Gallery featured in an exhibition called The Look.

“It’s one of my favourites from this exhibition,” says National Portrait Gallery Curator, Joanna Gilmour. “It’s Thorpey, he’s kind of in the zone, he’s standing behind the blocks, and he’s about to jump into the pool. And he doesn’t know it yet, but he’s about to set a world record and become the youngest ever world record holder in that particular event. He’s really just kind of completely unaware of the camera and completely himself.”

The Look includes works spanning five decades, ranging from a portrait of actor George Spartels, taken by Ivan Gaal in the early 1970s, to one...