Rio de Janeiro: The British duo of helmswoman Hannah Mills and Saskia Clark on Tuesday clinched gold in the 470 event on points ahead of Wednesday's medal race, leaving silver and bronze up for grabs for seven of the remaining nine teams.

Mills and Clark sit first with 28 points, a mathematically insurmountable 20-point lead over defending Olympic champions Jo Aleh and Polly Powrie of New Zealand.

The hard-sailing New Zealand women had their gold hopes shattered by two disqualifications, one for an unsporting failure to take a penalty turn after interfering with the Austrian 470 in the first race.

They powered back to the top after discarding the first DSQ, only to get another disqualification in the sixth race for a U-flag false start. With only one discard allowed, that was enough to put gold out of reach for New Zealand.

The rest of the pack is already nipping at Aleh and Powrie's stern. Only five points, less than a third place finish, stand between New Zealand and the next four teams in the hunt for the silver and bronze -- Tina Mrak and Veronika Macarol of Slovenia, Annie Haeger and Briana Provancha of the United States, France's Camille Lecointre and Helene Defrance and Japan's Ai Kondo Yoshida and Miho Yoshioka.

Sailors are awarded points equal to their finishing position in the preliminary rounds, but in the medal race, points are doubled. The sailor or boat with the lowest score at the end of the regatta wins.

In the men's 470, Croatian skipper Sime Fantela and crew Igor Marenic, Greece's Panagiotis Mantis and Pavlos Kagialis and Australia's Mathew Belcher and Will Ryan have guaranteed a place on the podium. With a 10-point lead over the Greeks, Fantela and Marenic are clear favorites for gold.