Specialist abseilers clambered down the 96 metre tall landmark and spent the day washing the clock face.
Every four years window cleaner’s abseil from the belfry and wash each clock face.
Time is spent inspecting and repairing cast iron joints and the opaque white glass in the four faces, all while hanging 60 metres from the ground.
Each seven metre diameter clock face has 312 panes which can often become damaged by pigeons and bell vibrations.
The clock will continue to keep time during the cleaning process, but the hands on the face being washed do not move.
Deputy keeper of the clock Steve Jaggs said: "Big Ben is one of the UK's greatest icons, and cleaning the Great Clock is a vital part of its maintenance.
"The process is complex and requires a real head for heights. We have an expert team who will ensure that the clock is thoroughly cleaned and that this piece of our national heritage is safeguarded for future generations."
