Mark Newnham says he will not be tempted to deviate from his plan to claim the three-year-old triple crown with Shadow Hero after the horse's brilliant Group One Randwick Guineas win.

Shadow Hero ($6) emerged from the pack to chase down Godolphin colt Microphone ($4.60 fav) by three-quarters of a length with Hobartville Stakes winner Brandenburg ($5.50) a close third.

Josh Parr turned in a faultless ride, angling off the fence approaching the home turn and picking off runs before Shadow Hero surged between runners to land the first leg of the triple crown.

"That was some win and he gave him a great ride," Newnham said.

"We'd discussed following the fence as long as he could but I said, look, you're going to have to make a decision to get out and get momentum

"Once he started to come I was confident he'd be the best finisher."

Shadow Hero disappointed as favourite in the Victoria Derby, finishing fifth, but Newnham was adamant the horse would stay.

He plans to give Shadow Hero the chance to prove him right in next month's Australian Derby (2400m), via the Rosehill Guineas (2000m), quashing suggestions of a Queen Elizabeth Stakes tilt.

"It's been the plan all along so I don't see any reason to change," Newnham said.

"He can come back for a QE next year. He's a gelding, he's here to race and I've got no worries about him staying the (Derby) trip.

"The best thing he does during any race is conserve energy and that's why he will stay."

Parr was ecstatic to claim a second Group One aboard Shadow Hero after the Spring Champion in October.

He had also been the regular rider of top colt Castelvecchio and had to choose between the two in the spring.

"I am so excited. I've got a lot of history with this horse and other runners and I stuck with this horse and this stable, they stuck with me and here we are," Parr said.

"These are the moments we all work for. We had a plan going into this race how we would attack it and it come off inch-perfect."

Microphone stuck on gamely after racing on the speed throughout, as did Brandenburg who jockey Rachel King felt was not as effective on soft ground.

"Huge run again. Get him back on a good track and he's going to win a Group One for sure," King said.

Castelvecchio finished eighth after getting well back making a mid-race move but kept trying to the line.

"We moved into it at the 700-metre mark and the horse finished the race off well, it just wasn't run to suit him today," jockey Kerrin McEvoy said.

"I'm sure that out in trip he can show more."