Lewis Hamilton has admitted that "time is slipping away" for him to realise his dream of becoming a multiple world champion.
The 28-year-old, who claimed his only title driving for McLaren in 2008, said that it takes "three or four" championships to be remembered as a great.
"Time is slipping away," Hamilton told the Sunday Times. "It's been five years since I won the world championship.
"There are a lot of drivers that haven't won a world championship, so I feel at least grateful that I have one, although one is less prestigious now because so many people have won a championship.
"Now the people who have two or three or four - [that's what] makes you special."
Hamilton is currently fourth in the standings in his first season with Mercedes.
