John Arnold was apprenticed to his father who was a watchmaker in Bodmin, Cornwall. In early life he appears to have been undecided whether to become a clocksmith and went for a while to Holland. He went to London and worked as a gunsmith, but finally settled as a clockmaker in Fleet Street. He obviously had great ability in minute metal work. In 1764 he made an exceedingly small repeating watch which he set in a ring and presented to George III, who was pleased to give him 500 guineas for his surpassing skill. From this date his reputation was established. It is interesting how many clockmakers become established by the act of special workmanship.

It is said that the Empress of Russia offered 1,000 guineas for a similar watch, which Arnold declined to make. Like others, he was most interested in the possibility of making a satisfactory chronometer, but by this time Harrison had secured the offered prize. He produced a number of pocket chronometers, some of which were tested at Greenwich.

He was admitted as a Member of the Clockmakers Company in 1783. He patented an isochronous helical balance spring with a spring detent escapement (at about the same time as Earnshaw). He took his son, John Roger, into partnership, who established a partnership with Dent. John Arnold died in 1799 and his son in 1843.

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