It’s the fourth consecutive year that the Tasmanian has taken victory on the hill-top finish, this year doing it in the ochre jersey for the first time and consolidating a lead which was the biggest ever for a Tour Down Under leader heading into this stage.
>> Struggling to get to the shops? Try 6 issues of Cycling Weekly magazine for just £6 delivered to your door <<
Porte attacked from just over a kilometre to go on the climb, with no-one able to match his power as the likes of Sergio Henao (Team Sky) and Esteban Chaves (Orica-Scott) slipped back down the climb.
Porte eventually finished with 20 seconds on the next rider home, Nathan Haas (Dimension Data), who initially looked to be in trouble on the climb but came from nowhere to rejoin the second group and out-sprint them all to the line.
With second place Gorka Izaguirre (Movistar) still suffering from the wounds of a crash on stage three and nowhere to be found in the final battle on Willunga, Haas has moved up to third overall behind second place Chaves.
The 151.5km stage saw some of the hardest racing of the week so far, and not just because of Willunga.
With a three-man break of Jeremy Maison (FDJ), Thomas De Gendt (Lotto Soudal) and Jack Bauer (Quick – Step Floors) still out in front with 1-55 over the top of the initial ascent of Willunga with around 23km to go, the likes of Team Sky, BMC and Orica began working extremely hard to pull them back and split up the race.
Will Clarke (Cannondale-Drapac) had initially been part of the day’s breakaway, which found a maximum gap of around 2-15, but the three who remained out there steadily began to see their advantage slip as the big teams turned the screw.
Sky and Orica particularly began to blow the race to pieces after the turn on to the flat road of McLaren Vale on the approach to Willunga, which saw the peloton completely strung out, and catching the break with 5km to go.
Sky then did a decent job of teeing up Colombian Sergio Henao, with his cousin Sebastian and Frenchman Kenny Elissonde doing big turns to support him on the initial slopes of Willunga.
That pace saw the likes of Haas dropped on the early parts of the climb, with and elite group of seven riders forming.
But no-one was willing to play their cards too early, with Porte the first to make an initial acceleration that was tracked by his rivals, before making his race winning move that no-one could follow.
It’s the 13th consecutive stage win by an Australian at the Tour Down Under and what will be the fourth consecutive overall victory for nation should Porte safely navigate the 90km Adelaide circuit race on Sunday and claim the ochre jersey.
2017 Tour Down Under, stage five: McLaren Vale – Willunga Hill (151.5km)
1. Richie Porte (Aus) BMC Racing Team, in 3-40-13
2. Nathan Haas (Aus) Dimension Data at 20 secs
3. Esteban Chaves (Col) Orica-Scott
4. Diego Ulissi (Ita) Team UAE Abu Dhabi
5. Jay McCarthy (Aus) Bora-Hansgrohe, all same time
6. Nathan Earle (Aus) UniSA-Australia at 23s
7. Rafael Valls (Esp) Lotto Soudal
8. Sergio Luis Henao Montoya (Col) Team Sky
9. Robert Gesink (Ned) Team LottoNL-Jumbo
10. Tom Jelte Slagter (Ned) Cannondale-Drapac, all same time
Overall classification after stage five
1. Richie Porte (Aus) BMC Racing Team, in 18-00-21
2. Esteban Chaves (Col) Orica-Scott at 48s
3. Nathan Haas (Aus) Dimension Data, at 51s
4. Jay McCarthy (Aus) Bora-Hansgrohe, at 54s
5. Diego Ulissi (Ita) Team UAE Abu Dhabi, at 59s
6. Rohan Dennis (Aus) BMC Racing Team, at 1:02
7. Rafael Valls (Esp) Lotto Soudal
8. Robert Gesink (Ned) Team LottoNL-Jumbo
9. Wilco Kelderman (Ned) Team Sunweb, all same time
10. Nathan Earle (Aus) UniSA-Australia, at 1:06