Godolphin's decision to head to Melbourne with Hartnell and bypass champion mare Winx has paid an immediate dividend with a PB Lawrence Stakes win at Caulfield.

Hartnell had the 1400m Group Two race at his mercy soon after jockey Craig Williams jumped the gelding from the barriers and had him tracking leader Charmed Harmony.

Turning for home, Williams slipped Hartnell some more rein where he quickly put the result beyond doubt.

Sent out the $2.80 favourite, Hartnell scored by 2-1/4 lengths from Charmed Harmony ($26) with Black Heart Bart ($3.60) a length away third.

The Godolphin team in Melbourne had earlier watched Winx, the world's highest-rated galloper on turf, make her winning return in the Warwick Stakes at Randwick.

Hartnell is rated Australia's second best galloper and David Charles, the Melbourne representative for Godolphin's Australian trainer James Cummings, congratulated the connections of Winx on her return win.

"It's fantastic that two signature horses for the spring have won first-up," Charles said.

"They're in New South Wales and we're in Victoria and at some stage we might meet again.

"But for now I think we'll just enjoy the day."

Charles said the Group One Makybe Diva Stakes (1600m) at Flemington on September 16 would be Hartnell's next assignment.

He said a decision on whether Hartnell heads towards the Caulfield and Melbourne Cups or tackles Winx in the Cox Plate would be made after that race.

Williams said Hartnell's win was better than it first appears as the gelding raced on his wrong lead leg.

He said the decision to bring Hartnell to Caulfield on Tuesday for a gallop was beneficial.

"If he didn't come here on Tuesday and have a look at the track, he probably still wins but I have more of a disagreement with him around the bend," Williams said.

"Today's win and the experience makes him a more seasoned horse here in Victoria."

Black Heart Bart, backed from $4.80 to $3.60, pulled up lame in the near hind leg.

Jockey Brad Rawiller was pleased with the performance.

"He was always going to be a little susceptible today with the wet ground," Rawiller said.

"But he's been set towards the Memsie so he'll improve greatly from this."