Stunned Londoners claimed to have seen a dolphin swimming in the River Thames on Sunday and Monday.

In video filmed on Sunday, ripples in the water are visible and a fin can be seen bobbing up above the surface near Putney Bridge in London.

The mammal was later identified as a harbour porpoise. According to local reports it was also spotted in Richmond and Kew.

Writes the filmer: "It was at about 14:45 and I was stood on Putney Bridge with my girlfriend. I had just taken a photo of her as the view looked so good. And just as I took it I spotted a fin. I thought I was seeing things at first and she thought I was crazy! It then kept popping up, swimming around in circles.

"We then went for a drink by the river and it kept swimming around in the same place for a good half an hour. When we left the pub, we then walked through Bishop’s Park (in Fulham) along the river and it appeared again, by this time there were people in small boats following it and taking photos."

The Metropolitan Police Service's Marine Policing Unit tweeted:
"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."

According to local reports, a baby dolphin was sighted in the Thames near Embankment.

++CLIENTS PLEASE NOTE: THIS VIDEO HAS BEEN LOOPED++

It was at about 14:45 and I was stood on Putney Bridge with my girlfriend. I had just taken a photo of her as the view looked so good. And just as I took it I spotted a fin. I thought I was seeing things at first and she thought I was crazy! It then kept popping up, swimming around in circles.
We then went for a drink by the river and it kept swimming around in the same place for a good half an hour.
When we left the pub, we then walked through Bishop’s park along the river and it appeared again, by this time there were people in small boats following it and taking photos.