For this chain-of-thought reasoning and answer, what was the question?
The relevant sentence in the passage is: The first speed camera was installed in 1991.
A: 1991
Q: The first speed camera was installed in 1991. A camera that was installed on the M40 motorway and recorded 400 instances of speeding within 40 minutes. The Association of British Drivers was formed the same year and campaigned vigorously against speed cameras.

Based on this passage, when was the first speed camera introduced in the uk?