Throw a spanner in the works
Meaning
To cause a disruption or unexpected problem.
Usage
Used when someone or something interferes with plans.
Origin & History
Origins and dates here are approximate summaries. Many idioms have disputed or unknown origins, and not every date has been checked against a historical dictionary, so treat specific dates and stories as a starting point rather than a citation.
Mechanical imagery from British workshops, where a spanner (wrench) jamming the machinery stops progress.
Used more broadly in twentieth century Britain, especially around factories.