Dissident has enhanced his reputation as a top-class weight-for-age racehorse with a gritty win in the Group One Makybe Diva Stakes.

On a day when champion Black Caviar delivered her first foal, trainer Peter Moody's latest stable star Dissident came to the party with his third Group One win and second in as many starts as a four-year-old.

Dissident put his rivals to the sword first-up with a convincing Memsie Stakes win, but this time the $2.70 favourite he had to show fighting qualities to hold off Caulfield Cup winner Fawkner ($10) to win by a half head.

"Fawkner definitely got level with him. I don't know whether he headed him but it was a tooth-and-nail battle and he put his head down at the right time," jockey Ben Melham said.

"When he got challenged half-way up the running, he lengthened stride and he showed the attributes of a really good horse."

Puissance De Lune ($7), runner-up last year, had to settle for third this time around as he finished another three-quarters of a length away.

Dissident has firmed to favouritism for the Cox Plate at $8 but doubts remain about the son of Sebring being as good over a middle distance as he has been at 1400m and 1600m.

"We will just give it time and let things settle," Moody, in Sydney for the Golden Rose meeting, said.

After sitting off the leader Messene, Dissident sprinted well at the top of the straight after getting a breather but was forced to fight hard as Fawkner issued a strong challenge.

"I don't think we learned a lot today about if he's a Cox Plate horse or is he going to be more effective at a mile," Moody's stable representative Jeff O'Connor said.

Melham is also in two minds.

"He's going to give himself every chance because he relaxes well. But whether he can physically stay the trip, I'm not sure" he said.

"If he can produce a turn of foot like that at a mile and a quarter, the world's his oyster."

Fawkner has moved to the second line of Cox Plate betting and his first-up performance delighted jockey Nick Hall.

"It was a fantastic effort first-up and I would imagine over further he is going to be better," Hall said.