A man filmed what he believed to be a dolphin yesterday, dipping in and out of the River Thames.

The mammal was spotted near Barnes Bridge, west London - and others claim they have seen it elsewhere along the river, looking lost in the capital’s waters.

Liam Le Roux said he came across the unusual creature at around 3pm on Tuesday (March 30).

Richmond and Twickenham Times: 'Dolphin' spotted near Barnes Bridge'Dolphin' spotted near Barnes Bridge

He said: “I was walking over Barnes Bridge and saw the disturbance in the water. I assumed it was a seal but then noticed the tail was quite different and more like a dolphin or porpoise.

“It swam around near the bridge for a few minutes and then was disturbed by a boat and headed back up towards Hammersmith.”

While dolphins are rare in London, they have been known to get lost occasionally in the Thames, which is 50 miles inland from the sea.

In the past, experts have attributed some of these ‘dolphin’ sightings to harbour porpoises, a similar looking breed of marine mammal.

Whatever the creature is, it seems to be turning heads this week, with further sightings reported near Tower Bridge.

On Sunday (March 28), a Twitter user appealed to the RSPA, saying:

“Dolphin, possibly a baby one, spotted in the Thames just passing under Tower Bridge towards London Bridge...I feel like it needs some help to go the right direction home!”

Another man filmed a 'dolphin porpoise' on Tuesday (March 30) travelling down the Thames. 

Environment experts at the London Port Authority suggested the animal was a harbour porpoise, which are "not uncommon" in the Thames.

A spokesperson said:

"From the pictures we've seen, our instincts are that it's a harbour porpoise. It's probably not a dolphin judging from its size and fin shape. It's still a beautiful animal but it's not uncommon in these areas."

The creature is obviously taking advantage of the turn in the weather. People should enjoy watching it, like all marine animals, from a safe distance."