* Britain's Lizzy Yarnold and Laura Deas grab gold and bronze.
* British women have won medals at every skeleton event since its Olympic reintroduction in 2002.
* Yarnold becomes first Briton successfully to defend a Winter Games title.
* Austria's Flock slips from first to fourth on final run (adds detail)
By James Pearson
PYEONGCHANG, South Korea, Feb 17 (Reuters) - Lizzy Yarnold became the first Briton to successfully defend a Winter Olympic title when she claimed the skeleton gold on Saturday as Laura Deas took bronze to completen the country's greatest day in the Winter Games.
Austria's Janine Flock had seemed set to spoil the party when her impressive third run of four sent her into the final round in the lead. Yarnold, however, piled on the pressure with a course-record final run and Flock made a series of mistakes that relegated her from first to fourth.
Germany's Jacqueline Loelling took the silver.
British women have won medals at every skeleton event since the sport was reintroduced to the Games in 2002 and their two on Saturday, along with a bronze for Izzy Atkin earlier in the freestyle skiing slopestyle, meant it is the first time the country has won three Winter Olympic medals in a day - beating their best of two in 1924.
An ecstatic and largely British crowd at the finish line whooped and cheered as an overjoyed Yarnold whipped off her helmet and screamed.
Yarnold finished 0.45 seconds ahead of Loelling, who had led after the first two runs, as her blistering track record of 51.46 seconds made the difference.
Skeleton races begin with an explosive sprint, with athletes then diving head-first onto a sled which accelerates down the ice at speeds of over 100kph.
A minus 14 degrees Celsius wind chill threatened to keep crowds away, but the event has been a popular spectator sport in Pyeongchang following the success of host country South Korea's Yun Sung-bin, who took the men's gold on Thursday.
At the finish line, many were entertained by Nigeria's Simidele Adeagbo, competing as part of her nation's first Winter Games delegation, who danced cheerfully despite consistently coming last.
Although the 36-year-old clocked some of the fastest start times across the four heats, she struggled with the track at Pyeongchang, regularly crashing into walls as she exited curves.
Reporting by James Pearson; editing by Mitch Phillips