Twilight Payment gave Irish trainer Joseph O'Brien a second triumph in the Melbourne Cup but victory was overshadowed by the death of 2019 Derby winner Anthony Van Dyck.
The 25-1 winner, ridden by Jye McNeil, led from start to finish and held on from Tiger Moth - trained by O'Brien's father Aidan - and Prince Of Arran.
Tiger Moth's stablemate Anthony Van Dyck, winner of the Derby at Epsom in 2019, broke down in the home straight.
The horse broke a leg in the incident.
"It is with sadness that we confirm that Anthony Van Dyck had to be humanely euthanised after sustaining a fractured fetlock during the running of the Melbourne Cup at Flemington," said Racing Victoria spokesman Jamie Stier.
The race, which usually attracts a crowd of about 100,000, was held behind closed doors because of the coronavirus pandemic.
It was a winning debut Melbourne Cup ride for McNeil and a seventh triumph for owner Lloyd Williams in the two-mile handicap that has a first prize of more than £2.3m.
O'Brien, 27, also landed the race at Flemington with Rekindling four years ago.
"The horse has got incredible heart. Jye gave him a fantastic ride and he has a huge will to win and he just kept on fighting all the way to the line," said the trainer.
Kerrin McEvoy, the rider of runner-up Tiger Moth, was fined A$50,000 (£27,000) and suspended for 13 meetings for excessive whip use in the closing stages.
- Feature: The truth behind racing tipster Prince Monolulu
- 'There's something about him' - trainer on Prince Of Arran
McNeil had his mount prominent throughout with Tiger Moth also to the fore in the early stages before settling back into third.
With five furlongs to run, the 23-strong field was well strung out and Twilight Payment had lengths to spare entering the closing stages.
Tiger Moth charged home late, but Joseph O'Brien again denied his father, as he did three years ago when Rekindling beat Johannes Vermeer.
"We both realise how hard it is to win on the world stage in these big, big races, but I am very lucky that I have been able to win a couple of big races," said Joseph.
"Dad has been very lucky, he has won a lot of big races, I'd be delighted for him if he had won, and I'm sure he is for me having won. We do our best on the track and whatever happens out there happens."
British challenger Prince Of Arran, trained in Newmarket by Charlie Fellowes, flew at the finish to be placed for the third year running after coming second last year and third in 2018.
Melbourne Cup result
1 Twilight Payment 25-1
2 Tiger Moth 11-2
3 Prince Of Arran 17-2
4 The Chosen One 40-1
- Small Axe Trailer: Sneak peak of Steve McQueen's powerful new drama
- Top Gear: Watch the boys race around a deserted theme park