Maintenance and cleaning work to the Westminster clock means the chimes will not be heard until September.
It includes the replacement of the bearings that sound the chimes on the hour and every quarter of an hour. The work is carried out every five years.
The clock will continue to tell the time, but its hands are being stopped for several hours so an alternative system can be installed.
The last bongs were heard at 0800 BST on Saturday morning.
A team of specialist industrial rope access technicians abseiled down the south clock face an hour later.
They began the task of cleaning and repairing the four faces of the clock seen by so many as a symbol of central London.
This latest work is the final phase of a programme of planned works preparing what is officially known as the Great Clock for its 150th anniversary in two years' time.
The clock earns its nickname from the 13.5 tonne bell that rings out the famous chimes.
It is named after Sir Benjamin Hall, the man who was Commissioner of Works when the bell was first installed in 1859.
The clock has been stopped accidentally over the years by weather, workmen, breakages and even birds, but technicians have always been able to get it going again.