McGrath (left) - World Cup best (Getty Images)

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Glenn McGrath ripped through the Namibian batting line-up as ruthless Australia cruised into the World Cup Super Six with a record 256-run win in Potchefstroom.

The African minnows had no answer to McGrath's brilliance, crumbling to a paltry 45 all out and the heaviest defeat in World Cup history.

McGrath finished with a remarkable seven for 15, another tournament record, eclipsing Winston Davis' effort for the West Indies against Australia at Headingley in 1983.

Namibia's total was also the World Cup's equal second lowest, behind only Canada's 36 against Sri Lanka eight days ago.

The win secured Australia's passage from Pool A, leaving India, England, Pakistan and Zimbabwe to fight it out for the remaining two places.

Australia have now won a record-equalling 11 one-day internationals in succession and will have the chance to make it 12 when they come up against England in their final Pool A game in Port Elizabeth on Sunday.

Darren Lehmann was also in record-breaking mood, clubbing 28 from the last over of the innings to move to his half century and take Australia to a formidable 301 for six.

That came after Matthew Hayden had earlier got the holders off to a blistering start with a rapid 88 from 73 balls and Andrew Symonds had weighed in with 59.

Namibia have bowled and fielded well to create a favourable impression throughout the tournament.

Yet even though they maintained their high standards and discipline, they still had little answer to combat Hayden once he started to play his shots.

The opener cracked three sixes and nine fours in a destructive knock that was ended when he attempted one big shot too many and became one of three Louis Burger victims when he was bowled.

Symonds picked up the innings as he shared in an 84-run stand with Damien Martyn but a dreadful run out mix-up led to his dismissal as both batsmen ended up at the same end.

Martyn fell soon after for 35 but Lehmann ensured the innings finished with a flourish with a savage assault on Rudi van Vuuren in the final over. He clubbed two sixes and four fours to move to an unbeaten 50 in breathtaking style.

It was a superb display of clean hitting that Namibia could not hope to replicate. The writing was on the wall from the very first over when McGrath had Jan-Berry Burger comfortably taken by Ricky Ponting in the slips.

Brett Lee also called his captain into action to remove Stefan Swanepoel but thereafter he had to take a back seat as McGrath moved in for the kill.

Adam Gilchrist was kept busy behind the stumps as Morne Karg, Danie Kuelder, Deon Kotze and Louis Burger all edged to the wicketkeeper. Gavin Murgatroyd was trapped leg before and Bjorn Kotze was comprehensively bowled. Only Deon Kotze (10) made it into double figures.

McGrath's fun was ended by Andy Bichel, who joined the attack to remove Melt van Schoor and Van Vuuren in successive balls.

Yet there was still time for one more World Cup record to fall with Gilchrist claiming two more catches to finish with six in the match.