Fly-half Madigan kicked all of the visitors' points at the BBVA Compass Stadium, while Saracens' Chris Wyles scored all of his side's 12 points. Five Irish players, Robbie Henshaw, Stuart Olding, Jamie Hagan, Mike Sherry and Tommy O'Donnell made their debuts in the win and O'Mahony, skippering his country for the first time, was pleased for them in particular.
"It is an away from home Test win and I am thrilled to bits for the boys who won their first caps that the rest of the boys got the win on such a special day," he said.
"I'm thrilled to bits for them, but the overall thing is we got a win away from home, it was a tough game and we expected nothing less.
"They have really improved over the last 12 to 18 months, they have been really pushing on. It was tough out there, the conditions were tough and the ball was really slippy."