INTERVIEW: Civil Engineer David Knight on why the Baltimore Bridge collapsed so quickly

Structural engineers around the world are waiting to discover the results of an investigation into how a boat collided with a suspended bridge which crumbled and collapsed within minutes. The container ship rammed into a major bridge in Baltimore, causing it to snap and plunge into the river below. So what caused the bridge to collapse so suddenly? David Knight is a structural and civil engineer who designs bridges, as well as being a specialist advisor to the UK's Institution of Civil Engineers.