He's won over 2000 races and used to ride for the Royal Family, but Edgar Britt didn't think he'd celebrate his 100th birthday.

"I didn't expect to ever live to be 100," Australia's oldest jockey said of his centenary on Wednesday.

He also didn't expect to be selected as the jockey for King George VI after the second World War, but another man's misfortune proved to be his gain.

When Harry Carr broke his leg in 1948, Britt was asked to step in, and was watched on many occasions by the current Queen and her sister Princess Margaret.

They're not the only monarchs for whom he's donned racing colours.

In a career that took him from Australia to India, Britain, France and the United States, Britt rode for various maharajas in India in the decade he spent there.

He won 1200 races during the 14 years he was in England, including all the English Classics, bar the Derby.

But before those victories, he also raced and lost to the legendary Phar Lap.

"I got close to him a few times," Britt told the ABC.

"All I could see was his big backside striding away."

Since retiring in 1959, he has lived in Sydney's northern beaches where he is expected to celebrate his birthday with family.