An investigation is taking place after a woman was dragged for 40m along a platform and under a train at Clapham South station.

The independent Rail Accident Investigation Branch (RAIB) said they are investigating the terrifying incident, which the young woman survived.

They said the train stopped normally on the platform and passengers boarded, on Thursday morning, March 12.

A member of staff, on the platform, signalled to the train operator to start closing the doors. Before the doors fully closed, one set was obstructed and reopened.

RAIB said the woman who had just boarded, and found that the available standing space was uncomfortable, decided to step back off the train to get the next one. But when the doors closed again, her coat got stuck between them.

The train operator was unaware of the situation and started to drive into the tunnel, while the woman was dragged along the platform.

The driver checked the platform camera, displayed in his cab, and saw passengers stepping aside and a person moving with the train. He applied the brakes.

But, before the train came to a stop, the passenger fell to the ground, off the platform edge and into the gap between the fourth and fifth carriages, having become separated from her coat. The train stopped after travelling about 60m.

She suffered serious injuries to her arm and head and was taken to hospital.

A spokesman said: "The RAIB’s investigation will seek to understand the sequence of events and will review the arrangements in place for safe dispatch of trains from London Underground stations and the risk arising from items becoming trapped in London Underground train doors."

The findings will be published once the investigation is completed.