Sweet Idea has finally ended a Magic Millions hoodoo for owners Luke and David Henderson with a Guineas victory at the Gold Coast on Saturday.

The Henderson brothers have invested heavily in the racing industry over the past decade achieving success at the highest level, most notably when they shared in the ownership of last year's Melbourne Cup winner Fiorente.

With a thriving real estate business at the Gold Coast where Luke is also a director of the Turf Club, the siblings have always coveted success in the Magic Millions.

But they had to wait until Saturday for Sweet Idea to realise their long-held ambition with the filly scorching to an all-the-way win in the Magic Millions Guineas (1400m).

The Hendersons raced No Looking Back who was first past the post in the Magic Millions Classic two years ago, only to controversially lose the race on protest to stablemate Driefontein.

Sweet Idea was runner-up to Real Surreal in last year's Classic in another frustrating result but the filly sparked raucous celebrations in the mounting enclosure when she scored on Saturday.

"In the spring we thought she was our shiniest bullet but then she bled at her first run back and we had to be patient," David Henderson said.

Sweet Idea will be aimed at the autumn carnival after giving trainer Gai Waterhouse the third leg of a winning hat-trick following earlier victories to Driefontein and Whittington.

"I'll let the dust settle and give her 10 days in the paddock then reprogram her for the autumn," Waterhouse said.

"She deserved to win because her lead-up form had been outstanding winning first-up at Wyong and repeating that performance here today."

Waterhouse also singled out winning jockey James McDonald for high praise.

"James has made the quantum leap as a rider since he arrived from New Zealand and he's only going to achieve more success in racing," she said.

McDonald said the key to Sweet Idea's victory was the filly's relaxed nature.

"She switched off today when I got to the lead then she kicked hard in the straight," he said.

"In the run she settled a lot better than last start at Wyong and she was really strong at the finish."