London Olympic organisers were left red-faced on Tuesday when a huge clock in Trafalgar Square marking the countdown to the 2012 Games stopped just hours after being unveiled at a glitzy ceremony.

英国伦敦本周二举办了隆重的2012年奥运倒计时钟揭幕仪式，而仅在数小时后，矗立在特拉法加广场的巨型倒计时钟意外停摆。伦敦奥组委官员可谓颜面尽失。

The countdown clock for the London Olympics is unveiled in Trafalgar Square in central London. Tickets for the 2012 London Olympics go on sale Tuesday.
The steel digital clock measuring 6.5 metres tall and five metres long froze with 500 days, 7 hours, 6 minutes and 56 seconds to go before the start of the Games.

It had been unveiled on Monday by London Olympic organising committee (LOCOG) chairman Sebastian Coe and four British Olympic gold medallists, coinciding with 6.6 million Games tickets going on sale.

"We are obviously very disappointed that the clock has suffered this technical issue," a spokesman for Swiss watchmakers Omega said in a statement.

However, a LOCOG spokeswoman laughed off（用笑摆脱） the malfunction¹, adding "it is not our clock."

Trafalgar Square is where Londoners gathered in 2005 to hear their city announced as winning bidders².

Omega said the clock, with its unique design for 2012, had been developed by experts and fully³ tested ahead of its launch.

"We are currently looking into why this happened and expect to have the clock functioning as normal as soon as possible," a spokesman added.

The clock's design draws heavily on the geometric（几何学的） lines of the 2012 logo and Greenwich Mean Time, organisers said.

Omega will also provide the timepieces for the Games, as they have done since 1932.