If you think someone is in cardiac arrest (unresponsive and not breathing normally):

1. Call 999 (put your phone on loudspeaker, the call handler will tell you what to do).
2. Start chest compressions (CPR).
3. If others are present, send someone to fetch the nearest AED (defibrillator).
4. Turn it on and follow the prompts.
   Continue CPR between analyses until help arrives or the person shows clear signs of life.

Dialling 999 is vital. Several UK ambulance services state that their emergency operations staff can direct 999 callers to the nearest defibrillator and may provide a cabinet code where necessary.