PSA: If you ever have to call 999, when the call is connected from the exchange to the relevant service's call centre, be aware that the first 5+ seconds will be the exchange operator telling the call centre what exchange the call was connected to, and what the phone number is.

It usually goes something like this, if the exchange was based in Glasgow for example:

Exchange op: "Emergency, which service?" Screaming caller: "(screaming) AMBULANCE!" Exchange op: "Connecting you now" Exchange op (to ambulance operator): "Glasgow connecting mobile (reads number)"

The call operator will not be able to talk to you until they have typed in the number from the exchange operator. This is so that if you are cut off, the emergency services can call you back. The problem arises when the caller is screaming/panicking (understandable though), and the operator cannot hear the exchange op telling them the number.

I've had it where I've had to shout at the caller to be silent several times so I can hear the exchange operator. Sometimes I've had full conversations with the exchange operator about what the caller has said because the caller is so distressed and has hung up.

Source: I used to be an ambulance 999 call taker (about 10 years ago so this may have changed).