A protected species created quite the splash when it was spotted swimming in the Thames this week.

Photographers and onlookers originally thought the finned creature was a dolphin but the Environment Agency confirmed it was a harbour porpoise.

The porpoise, whose Latin name is phocoena phocoena, was spotted swimming between Richmond and Twickenham bridges by David Chare, who captured the sight on his camera.

He said he only spotted one porpoise and it looked as though it could not get downstream, past the lock gate, which was closed on Monday, February 18.

The porpoise was seen the following day in the river at Putney and police patrolling the river let their Twitter followers know about the rare sight.

MPSonthewater ‏tweeted: “Had a few reports of dolphins in the water near Twickenham and Richmond bridges. Must be some ’fin’ about London they like #daytrip.”

Jules T-Smith wrote: “Apparently there are dolphins in the Thames near Twickenham. That’s pretty cool - saves me a trip to some exotic location.”

Porpoises are related to whales and dolphins but are distinguished by their shorter beaks, flattened spade-shaped teeth and more stumpy fin.

There are six species of the animals, which live in oceans and normally stick near shorelines.

RNLI volunteers pulled the dead body of a porpoise out the river in Chiswick in 2011.

In 2006 people were gripped by the plight of a whale that swam up the River Thames and died despite an attempted rescue.

Under UK law, whales, sturgeons and porpoises are royal fish, which means they are classed as the personal property of the monarch.

The law states that if species are discovered dead or in distress the Receiver of Wrecks must be notified along with the Natural History Museum.