The tower is built of coursed rubble masonry and contains four floors, connected by a spiral stone staircase (see diagram). The upper floors each contain part of the workings of the clock. The pendulum case is on the first floor, the clock room is on the second floor, and the bell room is on the third.
The clock faces are a later addition; they are at the second-floor level, connected internally to each other and to the clock mechanism by a steel spindle. Originally, the clock’s chiming was the only way to tell the time in the village.
The clock at St. John's at Hackney is an example of a relatively small group of English clocks, considered to date from the 1580s but continuing to be made to a traditional design until the end of the seventeenth century. Notable examples include the Dover Castle Clock (Science Museum), the Cassiobury Park Clock (British Museum) and the clock now exhibited at Clandon Park, Surrey. Although the St. John’s clock has been extensively altered … enough of its original fabric remains to justify its preservation. Its mention in the parish documents greatly adds to its historical importance, both individually and as a member of the group.
The clock is of historical significance, and has been dated to the late 16th or early 17th century. It was manually wound for over 400 years. Recently, auto winding has been installed to protect the mechanism. The Curator of Horology at the Royal Observatory in Greenwich says:
All the clocks mentioned above are believed to have originated from the same workshop. However, the maker’s name remains unknown.