A late decision to back up Cosmic Endeavour in the Canterbury Stakes reaped the desired result when the mare set a track record to win the Group One at Randwick on Saturday.

Cosmic Endeavour's victory capped a red letter day for trainer Gai Waterhouse who also claimed the two juvenile features at Randwick with new Golden Sipper favourite Vancouver and emerging filly English, as well as the Australian Guineas at Flemington with Wandjina.

"It has been a fabulous day, a day you dream about," Waterhouse said.

Her buoyant mood was in contrast to that of last weekend when results didn't go her way.

But it was that experience that led Waterhouse to reassess her plans for Cosmic Endeavour and switch her goal from next week's Coolmore Classic to Saturday's Canterbury Stakes.

"I was very despondent and down in the dumps after an ordinary day in both states last week," Waterhouse said.

"I started thinking about it and thought `this is the race for her'.

"The Canterbury Stakes is such a winnable race for mares like this. She is just hitting her hobbles and every single day this week she kept improving.

"She has beaten the boys before and I just knew she was cherry ripe and this was the time to run her."

With regular rider Tommy Berry already committed to rival Leebaz, James McDonald picked up the winning mount and gave a polished display.

The $3.30 favourite took up the running and kicked strongly to win by a half length over Catkins ($4.40) who looked to drop the bit at the top of the straight but rallied again late.

Criterion ($12) did his best work for third another three-quarters of a length away.

Trainer Chris Waller was proud of the effort of Catkins.

"She was out of her comfort zone and they've run a track record," Waller said.

Cosmic Endeavour stopped the clock at 1:15.17 for the 1300m trip, almost half a second faster than the previous mark held by As Needed.

Waterhouse was unsure where Cosmic Endeavour would run next but said the Doncaster Mile was among the options.

Sacred Falls showed he was on track to defend his Doncaster crown, closing late to finish fifth.