Local hero Simon Gerrans celebrated Australia's national day in style with a thrilling win in the fifth stage of the Tour Down Under on Saturday.

Gerrans flashed home to edge out Dutchman Tom-Jelte Slagter, who seized the overall lead from Welshman Geraint Thomas with another superb ride.

Gerrans, the 2012 champion from Australian team Orica GreenEDGE, sent the huge crowd at the finish line on top of Old Willunga Hill into raptures as he passed Slagter with 200 metres to go and held on to win his first stage of the week.

Slagter's second place was enough to see the Blanco Pro Cycling rider take the ochre leader's jersey from Thomas, who was well in contention until he ran out of steam 600 metres from the finish line.

Thomas slipped back to 17th place, 28 seconds behind the Dutchman, and now lies in fifth place in the general classification, well out of contention for overall honours with only Sunday's 90-kilometre (56 miles) stage on the Adelaide street circuit remaining.

Slagter, 23, had celebrated his first win as a professional when he won Wednesday's second stage to Stirling.

He is now almost certain to be crowned overall winner when the race finishes on Sunday, giving Blanco, formerly known as Rabobank, a win in their first race as a new team.

"This whole week has been amazing for all the team -- the first win for me and today I can hang this (ochre) jersey around my shoulders, it's amazing," he said.

Slagter said he hoped the success would help attract a new sponsor, following Rabobank's decision to withdraw funding in the wake of doping scandals.

"For everyone it's the first race so to go home with the stage win and hopefully the general, it's the best start you can have," he said.

"This is the best way to show to the Dutch people and the world how nice cycling can be and what we can do.

"I'm proud of the team and I hope we can find a new sponsor."

Saturday's 151.5-kilometre stage from McLaren Vale to the top of Old Willunga Hill saw the riders complete three circuits around Aldinga Beach before two climbs up the infamous Category One hill.

A group of seven broke away on the first of the three beach circuits and at one stage had opened a gap of over four minutes.

But the peloton picked up the pace and gathered them in right at the start of the first climb up Old Willunga.

Movistar's Eros Capecchi and Jose Herrada Lopez then attacked on the hill along with AG2R La Mondiale's Guillaume Bonnafond, and they were soon joined by Jurgen Roelandts from Lotto Belisol.

The four riders crossed the top of the hill 300 metres ahead of the peloton and opened a slight lead on the last circuit before the final climb.

However, the peloton closed again and the race was back together at the bottom of the hill, when the final attacks began.

Swiss rider Steve Morabito (BMC Racing), Portugal's Tiago Machado (RadioShack Leopard) and German Bert Grabsch (Omega Pharma-Quick Step) opened a small break, before Machado tried to go on his own.

With 800 metres to go Gerrans flew from the front of the peloton and passed Machado, only for Slagter to go past them both, leaving a spent Thomas in his wake.

However, Gerrans stayed on Slagter's wheel and delighted the fans when he overtook the young Dutchman.

"I've been really struggling with my asthma and today was the first day that my chest was clear," Gerrans said.