Western Australia 347 (Whiteman 104, Connolly 90, Cartwright 55, Short 50) and 376 (Cartwright 94) beat Tasmania 186 (Rocchiccioli 4-48) and 160 (Gannon 5-23, Rocchiccioli 3-55) by 377 runs

Needing an implausible 538 runs on a tricky surface, Tasmania lasted just 40.5 overs and were bowled out for 160 as they lost 5 for 18.

Gannon, a fringe bowler for most of his long career, starred with a five-wicket haul, while Rocchiccioli finished with 3 for 55.

WA cemented themselves as Australian domestic cricket's powerhouse after an almost flawless performance. It was only the second three-peat over the past 20 years and WA's first since the late 1980s. WA are the only team to have won three in a row concurrently in the Shield and Marsh Cup.

WA completely dominated all facets of the match, while Tasmania appeared overmatched having missed their chance of hosting the final after a last round loss to South Australia.

Tasmania appeared to be going through the motions until the second new ball, but Webster provided a much-needed tonic with a spectacular diving one-handed catch at leg-slip to dismiss Hardie for 47 off Jarrod Freeman.

Webster was in the thick of the action and rode a rollercoaster of emotions. He dropped Cooper Connolly at slip and was left exasperated when the bail did not dislodge after bowling a cracker to Cartwright that hit the top of off stump. The WA players on the team's balcony could not believe their eyes, with a few of them rushing into the room to watch a replay.

Webster made amends by holding on to an edge from Connolly as he threw the ball high in the air in celebration. Tasmania bowled a much better length and produced the type of disciplined effort they lacked for much of WA's first innings.

But Cartwright, who made a half-century in the first innings, defied Tasmania and continued his knack for the big stage having made a match-winning half-century in last month's Marsh Cup final. Cartwright was hoping to end a lean season with a century, but fell agonisingly short when Webster had the last laugh with a delivery that trapped him lbw on the stroke of lunch.

Tasmania had hoped to be batting in the second session, but were left frustrated by WA's more than capable lower order. Tasmania's earlier spark eroded as they toiled under the sun as WA's lead raced past 500.

But Tasmania were left spooked by the dismissals of Charlie Stobo, who was bowled by a delivery that crept low, and Paris that reared off the surface.

Tasmania's agony was finally over by tea, but they were soon reeling at the crease with Wade nicking off Gannon in the second over. The dismissal ended the red-ball career of Wade, who received a standing ovation from some of the WACA faithful.

Gannon and Paris bowled menacingly with the new ball as Jewell and Wakim fell in successive overs. WA sniffed a victory before the close, but Silk and Doran steadied the ship with a 62-run partnership. They managed to blunt the spin of Rocchiccioli and scored relatively quickly with WA boasting an expectedly attacking field.

But Silk and Doran succumbed as the sparse sprinkling of fans in the terraces - with many fans having earlier left for the AFL match at nearby Optus Stadium - suddenly were getting excited.

They were at fever pitch when Webster and Freemon fell in the same over from the unwavering Gannon as the extra 30 minutes was taken.

WA were not to be denied as Paris claimed a spectacular catch to seal a famous triumph.