Porpoises swim up River Thames
A pod of porpoises has swum up the River Thames to central London.
The Metropolitan Police Marine Policing Unit, which is following the group of mammals, tweeted that they "seem happy enough".
Initially the river patrol team, which tweets as @MPSonthewater, reported a sighting of a dolphin at Tower Bridge.
But further updates revealed the creatures to be harbour porpoises, which usually stick to coastal areas and river estuaries, but are known to venture further upstream.
The Marine Policing Unit tweeted: " Marine 2 are following a pod of about 5 harbour porpoises in the Lambeth area of the river."
It later added: "The porpoises seem happy enough. They are surfacing regularly and are staying in the Westminster area."
A spokesman for the Marine Conservation Society said: " It is unusual for five animals to be in the river though, as porpoises tend to be seen alone, and in smaller groups.
"It isn't possible to say whether the tidal surge is the cause of the porpoises being in the river, but it could well be related, either to the tidal movement, or as a response to the particularly rough seas beforehand. The outer Thames Estuary would have been relatively sheltered from northerly offshore winds.
"The pod should be able to navigate back to sea, and pass through the Thames Barrier when the tide goes out and the barriers are opened."