Sizing John claimed victory in a thrilling renewal of the Stan James Irish Gold Cup at Leopardstown.
Placed behind the mighty Douvan on no less than seven previous occasions, the seven-year-old formerly trained by Henry de Bromhead claimed his first win since joining Jessica Harrington in last month's Kinloch Brae Chase at Thurles.
Sent off at 100-30 for what was his first appearance over three miles, Sizing John travelled powerfully in a race not for the faint-hearted as a duel up front between Don Poli and Road To Riches ensured a searching gallop from the off.
As Road To Riches faded, Don Poli led the field into the straight, but Harrington's charge was travelling ominously well in behind and hit the front with a huge leap at the final fence.
His stamina was given a thorough examination as Don Poli and stable companion Empire Of Dirt attempted to bridge the gap, but Sizing John galloped all the way to the line to prevail by three-quarters of a length.
Empire Of Dirt narrowly beat 9-4 favourite Don Poli to the runner-up spot, with Carlingford Lough, winner of the last two renewals of the Grade One showpiece, only fourth on this occasion.