This single-dial clockworks was installed in the convict-built tower during the building period 1824-1830. There is some dispute about its origins. 

The late Jenny Gill wrote in 2016, “I have not found any shipping information that ties in with a repeated legend about the first clock and how it came to Launceston, which says; ‘In the bowels of a convict ship coming to  Van Diemen’s Land lay a quantity of iron  as ballast. This iron was assembled into a clockworks by a convict who was rewarded  with two years cut from his sentence.’  As for possible origins, it is not an English structure. It may have been made in Sydney, and that Reverend Youl had it sent down in the early 1820s.  It may have been a gift to Youl from Governor Macquarie or the Reverend Marsden, for services rendered in Sydney, and shipped over without record on one of the many Government vessels. The convict of the legend might have been one assigned to Youl and a bargain was struck. This would be in keeping with the generous nature of  Reverend Youl.”

The clockwork was superseded by the present mechanism with 3 dials (4th never used) in 1835. In the 1840s, there were failed attempts to sell the earlier mechanism. 

In the earliest colonial period, convicts and the poorer classes (the bulk of the population) would not have been able to afford personal clocks and watches. At the same time, both classes were required to work for specified hours. 

The clock at St. John's performed an important role as the town clock for much of the colonial period, regulating working hours and transport timetables. There was public acrimony when the clock (this one and its successor) failed to keep correct time, and the church felt that the clock, expensive to maintain, should be subsidised by the government and community.