One of the world's most powerful stables collected a rare and coveted Group One double on Saturday when Long John won the Caulfield Guineas in Melbourne and Complacent claimed the Spring Champion Stakes at Randwick.

For trainer Peter Snowden the wins ranked among his finest achievement - but he refused to accept more than 50 per cent of the credit.

Snowden, who was at Caulfield to see Long John triumph in a 300m slog to the line in the Guineas, said all praise belonged to his son Paul who manages the Melbourne "branch" of owner Sheikh Mohammed al Maktoum's worldwide Darley racing operation.

"I've only seem him gallop twice in his life," Snowden said.

"All credit goes to Paul."

Long John, the $3.80 favourite, rewarded a perfect Kerrin McEvoy ride with a hard-fought half length win over Divine Calling ($13).

Shamus Award ($21) came from last at the 400m to take third place, a further two lengths away.

Snowden praised Long John's courage to withstand Divine Calling's challenge that was laid down as the field turned for home.

"He had to dig deep ... to keep on fighting," he said.

"It was a very brave win by a very good horse."

The Cox Plate looms as a possible target for either Long John or Complacent, although a late entry fee of $130,000 would need to be paid for the latter.

If he races on this spring Long John will probably attempt to give Snowden a clean sweep of the major spring three-year-old races in the Victoria Derby.

"I'll think long and hard about the Cox Plate, but it's a big ask," Snowden said.

"The Derby might be a better option," Snowden said.

The temptation to run Long John in the Derby may be less pressing for Snowden than it has been in recent years when some of his best colts have been transferred to his owner's stables in Dubai and England.

But Long John is a gelding, removing the benefit in Sheikh Mohammed taking him abroad.

The Guineas proved a disappointment for most of the other fancied runners.

Second favourite Prince Harada ran on fairly to finish sixth, the New Zealander El Roca battled on for fifth after being on the pace and the well-backed Dissident held fourth after making a dash at the leaders at the 200m.