Country trainer Phil Atkins has upstaged the Golden Slipper winning team in the Gosford Guineas with outsider In Cahoots beating Chautauqua in atrocious conditions.

Trained by the Hawkes family partnership and ridden by James McDonald who combined with Mossfun on Saturday, Chautauqua was the $3.50 favourite to win the 1200m $250,000 race.

With rain falling all day, the form books were out the window with In Cahoots ($26) handling the heavy track to beat the favourite by half a length.

It was an emotional win for Atkins who prepares a small team at Maitland.

"It is my biggest win ever," Atkins said.

"I always thought he could win a decent race. I didn't want a heavy track but he obviously handled it well.

"I ride him all his work. And it's great for the owner Lee Rowan who has been with me for about four or five years now."

For In Cahoots' jockey Christian Reith, the win brought emotions of a different kind after a tough few days handling the death of his close friend and fellow rider Nathan Berry from a rare illness.

Reith, Nathan's twin brother Tommy and father-in-law Glyn Schofield, all rode at the Slipper meeting Rosehill on Saturday and travelled to Gosford a day later to fulfil their commitments.

"A lot has been said," Reith said.

"We're here for the family to support and love them as much as we can.

"It's fantastic to ride winners and Phil was confident leading into the race and the horse handled the track well."

A funeral service for Nathan Berry will be held at Rosehill Racecourse on Tuesday.