Horspool managed to extend his lead to around 100m by the 41km mark, at which point he was confident of winning his first Rotorua Marathon.
"Late on the race, the legs were feeling really good and, once you get 100m on somebody, you can hold the pace. I think I was running 3m20s (per km) at the end, so I knew they would have run run at least 3m 10s in that last K to pick me up, so I was just making sure I didn't go too deep and pop."
His winning time was 2h 27m 39s.
"It was a stunning day, cool to start with ... (the four of us) had a good pace, but I was happy to be in front for the last couple of Ks."
Sanson finished second, after being the first to drop off the back of the group.
He said he composed himself and knew that with 5km to go it was time to start his wind up. His time of 2h 28m 10sec was a personal best.
Third was Auckland chef Faherty, with Payne fourth.
The women's race looked to be heading to be a walk in the park for Texas based Kiwi Liza Hunter-Galvan, who dropped Mel Aitkin around the 10km mark, but dehydration and cramping slowed her over the last 10km of the race.
Hunter-Galvan won the Rotorua race in 2012 in a time of 2h 46m 23s. This year her winning time was 2h 55m 25s.
"I wasn't coming up for a speed record, but I did think I might break 2h 50m, and I think I might have been able to if I didn't dehydrate" she said. "My last 10 was a death march."
She had made the trip to New Zealand with the express intent of winning in Rotorua.
"I ran Boston last year and I feel Rotorua is the Boston of New Zealand. I'm going to run my last marathon this year, probably where I live, but what better way than to close it out and run a local (New Zealand) marathon."
Auckland's Katie Wyrill was second in 2h 57m 25s and Rotorua's Johanna Ottosson was third just 27 seconds behind.
The men's half marathon was won by Rotorua's Michael Voss in 1h 4m 55s with Cambridge's Alice Mason taking out the women's half in 1h 18m 31s.
