Shout for help, and shake the person gently.

Look and listen for signs of normal breathing.

Call 999 on loudspeaker and tell them the person isn’t breathing. The ambulance call handler will tell you where the nearest automated external defibrillator (AED) is. If someone is with you, ask them to fetch it and bring it back.

Interlock your fingers and start chest compressions twice per second. Don’t stop.

If a defibrillator arrives, switch it on and follow the instructions.

Continue CPR until:  
- the AED asks you to pause while it reanalyses and gives another shock if needed  
- a paramedic arrives and tells you what to do  
- the person shows signs of life.