Lord Coe has refused to call Michael Phelps the greatest Olympian of all time – despite winning more medals than any other athlete in history.

The 27-year-old claimed his 19th medal on Tuesday, and although the US swimmer is "up there", Lord Coe said he did not think of him as the greatest. "Evidently, by the medal tally, he's the most successful," said Lord Coe. "My personal view is that I'm not sure he's the greatest. But he's the most successful, that goes without saying."