Godolphin has denied Gai Waterhouse a second consecutive McKell Cup as reliable stayer Allergic produced a perfectly timed run to snare the feature race at Randwick.

Although Allergic gave the leaders a 10-length buffer at the 800m, the five-year-old gelding reeled in his rivals with ease on Saturday to push the Waterhouse and Adrian Bott-trained favourite Broadside into second.

Waterhouse scored the McKell Cup with Ecuador in 2016 before entering into a partnership with Bott.

Chris Waller's wait to win the Listed 2400m race continues after Soviet Courage ($31) was the best of his trio of runners in third, half a length further back.

Allergic, backing up from a second to Top Of My List in the Listed Lord Mayor's Cup (2000m) at Rosehill, benefited from a patient ride by Josh Parr and stablemate Big Blue setting up the home-straight surge.

"We were slightly worried when he was out the back there. There wasn't a huge amount going on in front of him but luckily Big Blue towed him into the race a little bit and gave him a nice run home," Godolphin Australia racing manager Claire Mackay said.

Allergic ($4.60) may head to Queensland for the Group Two Brisbane Cup (2400m) in a fortnight, although Godolphin representative Paul Reid said the Eagle Farm track was a deterrent.

A more likely target is The Metropolitan (2400m) in the spring at Randwick, where Allergic will attempt to improve on his third in 2016.

Broadside ($2.50) also has that Group One on his agenda.

Parr was rapt after Allergic hit the line out wide, saying he was ready to salute with 600m to travel.

"The stablemate took us a hell of a long way. I was confident a long way from home.

"He's got the runs on the board. I just had to point him in the right direction and he did the rest."