Tributes flow for legendary middle-distance runner John Landy, who has died at the age of 91.

The second man to break the four-minute mile barrier has been hailed for performing one of the most extraordinary acts of sportsmanship in athletics history, as well as his contribution to the community over several decades.

Australian John Landy, right, comes second to four-minute-mile great Roger Bannister. (AAP) Source: Supplied