She's one of the most photographed women in history and over the past 70 years has defined what it means to dress like a queen.

Not trendsetting or daring, but iconic.

She's become famous for her brightly coloured dresses and coats paired with a matching hat, accessorised with her signature square handbag, a string of pearls and a jewelled brooch. It sounds simple but the Queen's style has become a powerful formula.

It's a style that has been honed and refined over seven decades, helped by the close relationships she has developed with trusted designers and dressers.

"Royal fashion is fun, powerful and steeped with meaning," says author and royal fashion commentator Elizabeth Holmes. "Her image is a huge part of her legacy."

The Queen has always had a very clear idea of what she wanted to look like, says historian Michael Pick.

"People have said she has no idea about clothes, but that is simply not true. She is very astute about what suits her," Pick says.