Theatre-goers formed a human chain to block traffic to a busy London road after a couple were knocked down in a motorcycle crash.

Pedestrians were able to stop cars at each end of Waterloo Bridge using the lights on their phones, as an off-duty doctor came to the aid of the pair.

The couple, in their 60s, were then taken to hospital for treatment.

The woman suffered serious leg injuries, while the man had minor injuries.

Film producer Siobhán Daly was crossing the bridge at the time of the accident after leaving the National Theatre.

“When I arrived an off duty doctor was already helping, and saved that man’s life.He stabilised him, got him breathing and held his head before the emergency services arrived. He was a game-changer, so calm and kind under pressure,” she told the Evening Standard newspaper.

“I stayed and kept talking to the man about anything I could think of to keep him awake and also to keep him company so he didn’t feel alone.”

She added that to see so many people eager to help the pair made her realise “this is London.”

She said. “We hear so much about how bad it is but I just saw brave loving people and felt very proud that everyone cared so much and acted so selflessly."