What does Jonathan Betts say about the first mechanical clocks in medieval monasteries?

Jonathan Betts, senior curator of horology at the Royal Observatory Greenwich, said the earliest evidence for mechanical clocks comes from monasteries in central and northern Europe in the late 13th century, including Dunstable Priory in England in the 1290s. They were iron striking machines that rang the hours for night prayers and had no dials at first. Betts said they drifted by up to 20 minutes a day, but since a community shared one clock it hardly mattered.

• Latin records used the same word for sundials and clocks, so historians look for payments for oil or new ropes.
• Betts said most horologists accept the Salisbury Cathedral clock of 1386 as the oldest surviving.
• Dials arrived about a century later and were first divided into 24 hours.

Source: our own transcription of the episode. The full conversation is on In Our Time (2026-10-12). Read the whole episode summary →

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