At least 23 survivors had been located in one air-pocket of the collapsed building, while two more groups were located close by, bringing the total to as many as 50, says our reporter.

BBC: Dhaka building collapse: 'Large group' found alive

They regularly drop in on Mr Gold, who quizzes them closely, his wild greying locks and well-stuffed shirt pocket giving him the air of a rumpled physics professor expounding an exotic retail calculus.

ECONOMIST: Face value

The bullet, known as the Attenuating Energy Projectile (AEP), has an air pocket inside which disperses the force of the bullet across a wider area.

BBC: NEWS | UK | Police get 'safer' rubber bullets