Four fire engines and 21 firefighters and officers were called to a burst water main near to the entrance of a hospital on Euston Road, NW1, in the early hours of this morning.
The water levels have receded and firefighters have laid sand bags to protect the entrance to the building.
The Brigade was called at 0031 and the incident was under control at 0151. Fire crews from Holloway, Soho and Islington fire stations attended the incident.