The public is being urged to learn key first aid skills to help in the event of a terrorist attack.
A group of senior civilian and military clinicians has created a new app to help the public gain knowledge of how they can help those injured in an attack.
CitizenAID, which has received the backing of counter-terrorism police, including information on how to deal with limb loss, open wounds, broken bones and burns.
Brigadier Tim Hodgetts, who is part of the team who developed the app, explained: “CitizenAID is grounded in deep and practical experience.
“The underpinning concepts have been tried and tested in numerous multiple casualty incidents involving blast and gunshot casualties during conflict. The treatment recommended reflects those skills that can be applied by people without medical training to save lives.
“The value of these skills has been clearly shown through year on year improvements in survival from serious combat injuries. These ‘unexpected survivors’ have depended on advances in hospital treatment.
“But more than this, they have depended on the skills of individual soldiers to allow the patient to reach hospital alive. This compares directly to the ability of the public to intervene with life-saving intervention. It is the rationale for CitizenAID.
“We have a duty to transfer the hard won medical lessons from recent conflict to the wider benefit of our public.”
Perform chest compressions by positioning yourself with your arms straight in the middle of their breastbone and pressing down vertically on the breastbone. Press the chest down by 5-6cm (2-2½in) and release so the chest comes back up fully. This is one compression.
Repeat 30 times, at a rate of about twice a second (which St John's Ambulance says is around the speed of the song ‘Staying Alive’).
After 30 compressions, give two rescue breaths by pinching the victim's nose firmly. Take a deep breath and seal your lips around theirs. Blow into the mouth until the chest rises. Remove your mouth and allow the chest to fall.
Do this for as long as you can or until help arrives.
If the victim begins breathing on their own again, put them in the recovery position.
Pack the wound with items of clothing or loose fabric.
Apply pressure to the wound using a finger, knuckles or a fist and elevate the wound.
If part of a limb is lost or bleeding is uncontrollable, apply a tourniquet (see next).
Use a tie, scarf or tear clothing into strips and tie just above the bleeding area.
Use an item such as a pencil, stick or cutlery as a rod. Knot your tourniquet material to the rod and twist tighter until the bleeding stops.
Hold in place or keep holding onto the tourniquet.
A belt fastened around the area and pulled tight can also be used.
Do not submerge the whole body in water.
If possible, cover the burnt area with something non-fluffy, such as clingfilm or a plastic bag.
For broken arms, a square scarf can be folded to make a triangular sling or you can improvise using clothing. Tie or pin a tie into a sling, or tuck the arm into a rolled-up jumper edge or between the buttons on a coat or shirt.
For legs, pad between the legs using clothing or any other soft material available and tie the good leg to the broken one.
Chief Inspector Richard Harding, head of the National Counter Terrorism Security Office, told the BBC that the advice was crucial because when a serious incident, such as a terror attack, takes place, the first priority of authorities arriving on the scene will be to deal with those responsible for the incident.
He said: “They won’t have time to deal with the people who are injured and that gap is vital to saving people’s lives.
“So we are really interested in the concept of CitizenAID. It allows the public and people involved in very rare incidents like this to help themselves and help others and their loved ones survive the situation.”
New guidelines issued to police at the end of 2015 saw a change in priorities for authorities attending the scene of an attack, from tending to the injured to dealing with attackers.
CitizenAID also reinforces guidelines issued by the National Police Chief’s Council in 2015 on what to do if you are caught up in a terrorist attack.
People are advised to to follow the mantra “run, hide tell” - run away if you can, hide if this is not possible and, once safe, contact the police.
The UK’s current national threat level is set at “severe”, meaning that an attack is highly likely.