The Grasshopper Escapement by George Harrison

The Escapement is the mechanism whereby the power of the clock or watch,

be it from a mainspring, or in the case of grandfather clocks, the weights,

is allowed to 'escape' isochronously, or in equal time.

Without the escapement, the clock or watch would simply 'run wild.'

Grasshopper Escapement

There will be further explanations of the Grasshopper Escapement later,
but the Escapement shown below, The Double Three Legged Gravity Escapement,
is the exact type that's used on Big Ben.