Big Ben, the 147-year-old clock on the banks of the River Thames famous for its accuracy and chimes, stopped ticking for more than hour, and officials don't know why.
The problem occurred on Friday night, the start of a three-day weekend in Britain, silencing the clock near Parliament, an engineer at the palace said on Saturday.
The problem began at 10:07 p.m. when Big Ben's minute hand stopped. It began moving again slowly, then stalled a second time at 10:20 p.m. and remained still for 90 minutes before starting again, the engineer said.
Some speculated that hot weather may have been to blame. Temperatures in London reached a high of 31.8C on Saturday, and forecasters called it England's hottest day in May since 1953.
But the engineer at the Palace of Westminster, which operates the clock, said the cause was unclear. "We've been told there was a minor glitch, but then it was started up again," he said.
The Big Ben is renowned for its accuracy and even survived attacks by Luftwaffe bombers during the Second World War, continuing to mark the time within one and a half seconds of GMT.
However, it has had problems from time to time.
In 1962, snow caused the clock to ring in the New Year 10 minutes late, and in 1976 the clock stopped when a piece of its machinery broke. Big Ben also ground to a halt on April 30, 1997, and once more three weeks later.
Big Ben is the name of the clock's 13-ton cell, which was named after Sir Benjamin Hall, the British commissioner of works at the time of the clock's construction.
The official name for the Gothic tower in which Big Ben nestles is St. Sephen's Tower Standing 100 metres tall, it was completed in 1858, after a fire in 1834 destroyed most of the Palace of Westminster.
