Journey of a 999 call
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When the 999 service was introduced 75 years ago, it was the world's first emergency number.
Last year, the number was dialled 37 million times, with more than 98% of the calls answered within five seconds by operators.
Genuine calls are put through to the emergency services, which then try to get responders to the scene of an incident less than 15 minutes after the 999 call was first made.
Video produced by Joseph Coulson.