Radio 4’s PM programme spots the clanger as the bongs of the Palace of Westminster bell fall out of time

For those who set their watches by the bongs of Big Ben comes unsettling news: the clock has been running at least six seconds fast.

The mismatch was first spotted by Radio 4’s PM programme, which alerted the keeper of the great clock to the problem. The clock is believed to have been out of time for around two weeks.

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PM presenter Eddie Mair said it was not uncommon for the start of the chimes – which ring in 6pm at the end of the early evening Radio 4 programme – to vary. But, he told listeners on Monday, “of late Big Ben’s been even more erratic. The earliest the chimes start is usually 27 seconds to six [pm], but one day the other week it was seven seconds sooner.”

Steven Jaggs, the keeper of the great clock, and Ian Westworth, one of three expert clocksmiths working in the Palace of Westminster, were hauled in to explain the disruption to the fabric of time and radio listeners.

“This is a mechanical clock,” Jaggs pointed out. “It’s not digital, it’s not electronic. It does take a lot of love and care.”

Clocksmiths already climb the 334 stairs of the Elizabeth Tower three times a week to wind the clock, whose timing can be affected by the weather, atmospheric pressure or simply by being 156 years old.

Westworth said he and his team had been up to the clock “most days” since they learned of the problem, trying to put it right.

“To tell you the truth, we don’t actually know why it happened,” he told Mair.

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“The error started building up and it went slightly unnoticed over a weekend … You can’t just wind the hands forward or wind the bell forward to make it catch up those five or six seconds that it was wrong.”

The recalibration involved taking weight off the pendulum to slow it down again. In fact, Westworth revealed, the work to bring the clock back on time encouraged Big Ben to correct itself, causing it to run slow.

“It’s settled down now,” he said, cautioning, however, that such a “temperamental” clock would continue to be likely to lose the odd second here and there without warning.



The Radio 4 pips remain impervious to the unreliability of Big Ben. The six beeps at the top of each hour are timed from an atomic clock housed in the basement of the BBC’s Broadcasting House.