Police are appealing for witnesses and information after a man fell into the River Thames at Westminster Bridge.
Police were called to a man in the water near Westminster Bridge at about 5.45pm on Friday.
Police officers from Westminster attended the location, as did the Met's Marine Support Unit, the Coastguard and the police helicopter.
Although the man was briefly seen in the river near the bridge, it is thought he was then swept along by the current and disappeared.
He is described as a white man with black dyed hair with grey roots and a grey beard. He was wearing a dark coat with two badges on the left lapel. He is thought to be around 6ft tall and slim.
No body matching this description has been recovered from the river and there are no reports of any missing people connected to this incident.
Officers have serious concerns for the welfare of this man and are appealing for anyone who saw a man matching this description or a man falling from the bridge to contact Westminster CID via 101 or @MetCC.