Some of the famous chimes of The Great Westminster Clock have been silenced for a month while maintenence work is carried out.
Quarterly chimes will stop for about four weeks
Big Ben at Westminster Palace will continue to toll on the hour.
But the familiar "ding dong, ding dong", usually heard ringing out across Parliament Square on each quarter hour, was stopped at 0800 BST on Monday.
The work is expected to take four weeks and is the first major repair needed on the bells for about 50 years.
A new bearing will be fitted to the yoke of the fourth quarter bell at Whitechapel Bell Foundry.
Last October the chimes were silenced for 32 hours - believed to be the longest time in more than two decades - while engineers inspected the clock.
The chimes were hushed for longer in 1983 when the clock's hands were removed for new gilding to be applied.
Edward John Dent's clock, installed in St Stephen's Tower, at the northern end of the Palace of Westminster, became operational in 1859.