William Hamilton Shortt (1881–1971) was a railway engineer and noted horologist, responsible for the design of the Shortt-Synchronome free pendulum clock, a widely used time standard, employed internationally in observatories in the period between the two World Wars.

Shortt met Hope-Jones in 1910, and began collaborating in the design of master clocks from 1912, joining the Synchronome Company as a shareholder and director.

He produced a series of designs involving new forms of escapement, attempting to optimise the delivery of energy to the pendulum, while taking account of variations in external factors such as temperature and atmospheric pressure.

[2] Shortt's experiments continued until 1916, when he was released from duties with the LSWR to serve as a captain in the Royal Engineers in France.

Championed by the Astronomer Royal of Scotland, Ralph Allan Sampson, Shortt's free pendulum clock was rapidly adopted worldwide by many observatories as a time standard, and remained as such until the widespread adoption of quartz clocks from the Second World War onwards.