Meaning
To disrupt a plan or process by introducing an unexpected obstacle. The phrase is especially common in British English; American English often uses “throw a wrench in the works.”
Origin
A spanner is a British word for a wrench. The image is of a metal tool falling into moving machinery and jamming its mechanism. The expression developed from industrial mechanical imagery rather than a single documented accident.
Examples
The supplier’s delay threw a spanner in the works.
We were ready to launch, but a legal issue threw a spanner in the works.
Don’t let one bad review throw a spanner in the works.
Frequently asked questions
What does 'Throw a spanner in the works' mean?
To disrupt a plan or process by introducing an unexpected obstacle. The phrase is especially common in British English; American English often uses “throw a wrench in the works.”