Hartnell gained a decisive success in the AUS$1.5-million Group One The BMW over a mile and a half at Rosehill Gardens, Australia, on Saturday, March 28.
The Authorized four-year-old, partnered by James McDonald, was well away and pulled slightly in the early stages.
He settled in fifth on the inside as a good pace was set up front before being positioned off the rail around half-way.
Hartnell progressed to fourth before the straight and swung four-wide turning in, soon disputing the running.
Asked to assert, he ran on well and went clear to beat the Japanese challenger To The World by a length and a quarter in 2m 29.50s on good turf.
Trainer John O’Shea said: “Hartnell did a marvellous job as he didn’t have a lot go his way in the run.
“In the barriers, the horse next door reared up and tapped him and then in the run another horse in front of him had to be pulled out of the race.
“James made a long run on him from 600 metres out and Hartnell outstayed the Japanese horse who is no slouch for a very exciting and impressive win.”
Plans for Hartnell’s next race will be finalised this week.