Potential gang members are being offered lifesaving first aid lessons, so they can help with victims of attacks.
The classes are being taught by volunteer doctors and medical students.
The youths are learning techniques such as stemming blood-loss with a tourniquet, perhaps from a belt, so they can keep causality victims alive till medical help arrives.
The Street-Doctors group believes that they can equip them with skills to help prevent victims from dying.
More top news
The high of 35C was recorded on a Bakerloo line train between Piccadilly Circus and Oxford Circus at 2pm.
Weather forecasters say temperatures could reach 35C, beating the previous record of 34.6C in the scorching summer of 1976.
After years of political manoeuvring over the future expansion of Heathrow Airport, there has been an important development this lunchtime.