Story highlights Singh is the oldest person to complete a marathon

He totals eight completed marathons after starting at 89

Singh was born in rural India in 1911

He took up running after the death of his wife and son

Fauja Singh finished dead last at the Scotiabank Toronto Waterfront Marathon on Sunday.

But even though it took him eight hours, he had every reason to beam.

By completing the 26.2 mile course, Singh -- nicknamed the Turbaned Tornado -- became the oldest undisputed runner to finish a marathon.

He is 100.

Singh, born in rural India in 1911, did not start running marathons until he was 89, after he moved to England following the death of his wife and son.

He's completed eight now.

"He says no one is forcing him to do it. It's his desire to do it," coach and translator Harmander Singh said Sunday in an interview with CNN affiliate CBC. "He wanted to do one when he's 100 and today's the day."

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Singh was a colorful sight as he started the race in his canary yellow turban and a matching T-shirt with the words " Sikhs in the City" printed across its front -- a nod to his faith.

He finished more than six hours behind winner Kenneth Mungara of Kenya, who won the event for the fourth straight year.

Then again, Mungara is only 38.

Singh, the centenarian, already held the World Record for the 90-plus age group, completing the same race in 2003 at age 92.

But until now, the title of "oldest" was the cause of some debate.

The Association of Road Racing Statistician already recognized Singh as the oldest for a marathon he ran at age 93. But the Guinness Book of World Records listed someone else -- Dimitrion Yordanidis, 98, who ran in Athens in 1976.

Singh says his secret is a life without alcohol and smoking, a vegetarian diet of curries and tea, and daily exercise. He walks or runs up to 10 miles a day.

"I have said it before: that I will carry on running, as it is keeping me alive," Singh told the marathon website.