Thames 'dolphin': Londoners stunned as porpoise swims 40 miles down river

Londoners were left stunned after spotting a porpoise which swam 40 miles up the River Thames.

The lost mammal was initially thought to be a dolphin and sparked excitement on the banks of the river as people stopped to take photos and video footage.

The animal, which was later identified as a harbour porpoise, is being tracked by the RSPCA.

It was spotted 40 miles inland and from the banks of the Thames in Putney Bridge, Kew and Richmond.

It is thought to be the third time a dolphin or porpoise has been sighted in the Thames in nine months.

MPS on the Water, the Met Police’s marine team, said online: “We're aware a harbour porpoise has been spotted up at Kew.

“It's perfectly fine so please don't approach it as it's likely to beach itself.”

Its fin was visible as it swam about the river on Sunday and Monday.

Crowds gathered to watch the mammal, while rowers took close-up videos from their boats.

In May this year an ex-Olympic swimmer recorded what appeared to be a dolphin in the Thames in Richmond.

A baby dolphin was also sighted in February close to Embankment pier.