Australian sailor Tom Slingsby has virtually guaranteed himself a gold medal in the single-handed Laser class after winning both races on Saturday.

The results mean that Slingsby, from Gosford, on the Central Coast, has only to finish seventh or better in the medal race on Monday to outscore his nearest challenger, the Cypriot Pavlos Contides.

Australia's Tom Slingsby sails in the eighth race of the men's Laser class at the London 2012 Olympic Games in Weymouth and Portland. Credit:Reuters

Elsewhere, Australia's 470 class pairing of Mathew Belcher and Malcolm Page also won both races to reinforce their lead, while the Elliott match racing team of Olivia Price, Nina Curtis and Lucinda Whitty completed the opening round robin series unbeaten in the 11 races.

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Nathan Outteridge and Iain Jensen also lead the 49er skiff class.

For the time being at least the sailors are on course for three, possibly four, golds.