The win was also a first for trainer Danny O'Brien with Vow And Declare crossing the line ahead of Master Of Reality, Prince Of Arran and Il Paradiso.

A protest on behalf of the fourth-placed Il Paradiso, against the runner-up for interference over the final 100m, was upheld.

The decision relegated the Frankie Dettori-ridden Master Of Reality to fourth with Prince Of Arran gaining second and Il Paradiso promoted to third.

Williams famously missed the winning ride on the French-trained Dunaden in the 2011 Melbourne Cup because of suspension.

Read more: All the photos from Melbourne Cup Day in the Illawarra

Eight years later, Williams joins Neville Sellwood, Roy Higgins, Pat Hyland, Mick Dittman, Jim Cassidy, Damien Oliver and Chris Munce as the only jockeys to win the "grand slam" of Australian racing - the Golden Slipper, Caulfield Cup, Cox Plate and Melbourne Cup.

"It's great to be associated with a great horse like this horse," Williams said.

In a desperate finish involving four horses, the Danny O'Brien-trained Vow And Declare took an inside run and put his head down when it counted to win in a photo finish.

The margins involving the placegetters across the line were a head between first and second with a nose to third.

For O'Brien the win was one that meant everything.

The trainer was involved in a protracted battle with officials over a cobalt case which he eventually won but the process took its toll on his business.

"It doesn't get much better than this," he said.

Runner-up in the Caulfield Cup, Vow And Declare started at $11 with Prince Of Arran at $17 and Il Paradiso a $15 chance.

Rostropovich was last of the 24 runners.

First past the post:

AAP