Horse racing: Reigning Cox Plate champion Sir Dragonet dies

Jockey Glen Boss aboard Sir Dragonet after winning the Cox Plate in 2020. Photo / Getty

Reigning Cox Plate champion Sir Dragonet was sadly euthanised at The Valley on Saturday morning after breaking down in a track gallop.

Unfortunately the Ciaron Maher and David Eustace-trained Sir Dragonet sustained a catastrophic injury and could not be saved.

The dual Group 1 winner was among several Cox Plate contenders to spin around The Valley on Saturday, including favourite Zaaki, Verry Elleegant and Gold Trip.

Sir Dragonet defeated Armory and Russian Camelot in the $5m Group 1 W.S Cox Plate last year.

The Irish import trained on to win the Group 1 Tancred Stakes in Sydney in the autumn.

He was on track to defend his Cox Plate crown third up after runs in the Makybe Diva and Turnbull stakes.

"It is with great sadness to report that Cox Plate champion Sir Dragonet has been euthanised after tragically breaking down in a track gallop this morning," Moonee Valley Racing Club posted on Saturday morning.

"The MVRC passes on its condolences to @cmaherracing and all connections. Forever remembered as a Cox Plate champion."

Sydney jockey Glen Boss was due to arrive in Melbourne next week to partner Sir Dragonet's title defence.

The incident reportedly occurred in Sir Dragonet's warm-up at about the 800m mark.