NEW YORK -- A United Nations officer thought running the New York City Marathon was so nice he did it twice.

Kevin Shelton-Smith ran 26.2 miles in the morning before the official race started, then covered another 26.2 miles along with the rest of the field in the actual marathon.

"I'm always looking for a new challenge to find the limits of my body -- to be all you can be," said the 43-year-old Englishman, a peacekeeping air operations officer for the UN and an accomplished marathoner.

Shelton-Smith started in Central Park at 5 a.m. ET and ran the course from the finish line to the start, stopping along the way to talk with race volunteers. He reached the race staging area at Fort Wadsworth on the Staten Island side of the Verrazano-Narrows Bridge in 3 hours, 45 minutes.

That gave Shelton-Smith about 90 minutes to rest before taking off with the rest of the 35,286 entrants at the official starting time of 10:10 a.m.

Running conservatively at the start to feel stronger in the later stages of the race, Shelton-Smith finished the official marathon in 3:35:45. Last year, he finished the marathon in 2:47.