That left Elvira or Dunne needing an albatross on the 18th to force a tie but that was too tall an order with Dunne getting a birdie to pip the Spaniard to second place. I felt that tension. I hit the ball fantastic.
Warren closed with a 69 to finish on 15-under, eight shots ahead of the next best Scot, Stephen Gallacher, as he shot a third 70 in the event.
"Everything feels good, the game feels great, I just didn't pick shots".
"I will keep doing what I am doing - get through this evening because I am a little bit disappointed - but Spain has a great champion in Jon and I am sure he will win many more of these". I tried to isolate myself, but I could feel it.
The performance is one that Dunne can be optimistic about, a win is what he wants but falling short to a golfing prodigy and beating him for three out of four days is impressive.More news: Google AI experiment has you talking to books
The 23-year-old, in his first appearance at the Open, becomes the sixth Spanish golfer to win the tournament since it became a European Tour event in 1972. He needed to go super-low on Sunday to have any hope of snatching his first European Tour win and set out in ideal fashion with a trio of opening birdies.
"When I made the decision to come straight from Augusta it wouldn't be to just show up and walk around, I wanted to win this tournament", Rahm said.
Elvira holed a birdie from a similar distance at the same hole and moved alongside Rahm by draining a 35-footer at the 14th, where Dunne slipped three behind with a poor chip and bogey-five.
In-form Jorge Campillo completed a strong week at his home Open de España with a closing 3-under-par 34-35=69, nudging two spots up the final leaderboard to tied fifth on 15-under 273. Dunne also birdied the last to beat Elvira by one, with South Africa's Gerry Coetzee finishing fourth a further shot back after his 63 equalled the lowest round of the week.
Rahm won the rookie of the year award last year and finished third on Europe's Race to Dubai.