In the 1750s, Thomas Mudge, the renowned clock-, watch- and chronometer-maker, began work on a new escapement that was to become, in a modified form, the standard escapement for portable timekeepers up to and including the modern mechanical wrist-watch. It is now believed that this clock contains Mudge's first lever escapement. At that time there was great debate between those who felt that longitude could be found at sea by a timekeeper and those who believed that lunar observations held the answer. This clock is of particular interest, not only in having a balance-controlled lever escapement which would function at sea, but also in having a lunar indication which, at the time was the most accurate ever made using mechanical gearing. Even today it is still the second most accurate.
Towards the end of the eighteenth century the renowned astronomer James Ferguson calculated the theoretical accuracy of the lunar gears and found Mudge's work to be within 0.2 seconds per lunation (29½ days). A 7½ minute train-remontoire imparts a more constant force to the escapement, and two brass and steel laminated strips act on the two balance springs to compensate for changes in temperature.
It is thought that Mudge made this experimental clock with the intention of submitting it to the 'Board of Longitude' for the longitude prize, before deciding that it was not good enough.
In the nineteenth century the clock was owned by the celebrated civil engineer, Isambard Kingdom Brunel (1806-59).