Possible "transplant"

Major Surgery for Big Ben

The great clock has stopped twice over the past three weeks. Engineers investigating a problem in a key part of the clock's mechanism have decided that it will have to be stopped for a day while they examine the equipment causing the problem.

A shaft might have to be removed, and it will take another day's stoppage for the mechanism to be re-assembled. It might have to be stopped again for a further day if new parts have to be installed.

The latest breakdown was last Tuesday when the hands ground to a halt just before 4 pm. Then, after about 50 minutes, the hands were "fast-forwarded" to the right time, donging in quick time as they went round.

A familiar London landmark

Three weeks earlier, Big Ben stopped at 12.11 pm on April 30, less than 24 hours before polling stations opened for the General Election. It was stuck at this time for nearly half an hour, and then Big Ben struck 12.15 pm when the real time was 12.42.

Remedial work was carried out on Big Ben in 1994 after it stopped for several hours. The problem was identified as the gearshaft that controls the hour and minute hands of the clock's four giant faces.

Engineers said the ageing system had been showing clear signs of wear and tear. Like any elderly timepiece, Big Ben, now 150 years old, has suffered periodic problems.

After a breakdown in 1993, the chimes which strike the quarter-hours were silent for eight weeks while repairs were carried out.

Once a schoolboy visitor dropped a pencil in the works causing untold damage and costing an immense amount of money to put it right.