The Trek-Segafredo rider regained the crown he last won in 2017 as Britain's Matthew Holmes collected the stage win.

South Africa's Impey, riding for Mitchelton-Scott, grabbed the leader's ochre jersey from Porte after yesterday's penultimate stage and had a two-second lead over the Australian going into the final 151.5-kilometre route from McLaren Vale to Willunga Hill.

Porte's name has become synonymous with the stage's climb to the finish, with today being the first time in seven years he has not won the concluding leg of his home Tour.

Lotto-Soudal's Holmes caused a major surprise by not only staying with the home star, but also beating him to the line.

Impey was dropped during the ascent, however, and that was enough for Porte to win overall.

"It would have been nice to be the king of Willunga Hill again but I'll take the ochre jersey any day," Porte said.

"That last 800 metres today bloody hurt. 

"It was probably the most painful 800m of my life.

"Obviously, you don't get to take it in too much because you're in a different world of hurt. 

"But the crowds here are just second to anything really, it's like a Tour de France stage to be honest." 

Porte's overall time was 20 hours 37min 8sec.

Italy's European road race champion Diego Ulissi, who was sixth today, finished second behind him in UAE Team Emirates colours, 25 seconds adrift.

Third overall went to Germany's CCC Team man Simon Geschke, on the same time as Ulissi.

Impey had to settle for sixth, 30 seconds back, after ending today's stage in 20th place.

Holmes clocked 3:24:54 to win today and came home three seconds in front of Porte.

Italy's Manuele Boaro, riding for Astana, was four seconds behind the winner in third.

"Everyone's got power meters and you know everyone is on the limit so I just rode hard and sensible and then just had to go with Richie when he came past," Holmes said.

"He was obviously going a hell of a lot quicker than me up there, so he had no sprint left."

The race was the first leg of the International Cycling Union World Tour season.

Focus now turns to the one-day Great Ocean Road Race also in Australia on February 2.