Big Ben's chimes are stopped to allow work on St Stephen's Tower clock and bells.
The hands of the clock on St Stephen's Tower are moved to the 12 o'clock position while maintenance work is carried out.
Engineers are replacing rubber hammers on the hour bell and three of the quarter hour bells.
A Westminster engineer holds a worn hammer seal of Big Ben and two replacement seals.
Trainee clock mechanic Huw Smith makes adjustments to the settings of the clock.
The clock is expected to restart at about 1600 GMT on Sunday, ending its longest switch off in 22 years.
The stopping of the clock coincides with the end of British Summer Time and the start of Greenwich Mean Time - clocks have gone back an hour.