No Melbourne Cup runner has come under more scrutiny than Spanish Mission with the race second favourite going through a series of vet checks in the past week.

But Williams said his mind had been put at ease once and for all when he rode Spanish Mission on Sunday morning.

"After sitting on his back yesterday I had no concerns," Williams said.

Spanish Mission, one of two international runners in Tuesday's race, is the horse tipped to offer a serious examination of Incentivise's bona fides over 3200m.

It's an assessment based on the best northern hemisphere endurance form with Spanish Mission often mixing it with Europe's elite.

Since contesting the Dubai Gold Cup in March, Spanish Mission has been faultless at the highest level in the UK with a Yorkshire Cup success and placings in the Gold Cup at Ascot and the Lonsdale Cup at York.

In spite of coming off second best, Spanish Mission's Lonsdale Cup duel with the decorated stayer Stradivarius in one of the race's of the English flat season confirmed a trip to Melbourne.

"The stable is very bullish about his chances and I can understand why after having my first sit on him yesterday," Williams said.

"He's a beautiful horse to do anything with for a rider.

"He's got a lovely action and it feels like he's got good change-up speed as well, which would be really helpful in tomorrow's race."

Spanish Mission is an anomaly among the overseas staying ranks because he runs his best races on firm ground.

And he looks certain to have conditions to his liking at Flemington with the track rated in the good range and no sign of rain.

Williams will be chasing his second Cup win after lifting Vow And Declare across the line in 2019.

Australian Associated Press