The whale spotted swimming around in the River Thames near the Houses of Commons is probably a species of Northern bottle-nosed whale experts have said.
Richard Sabin, an expert on whales and dolphins at the Natural History Museum confirmed that the mammal was a Northern bottle-nosed whale, Hyperoodon ampullatus.
Earlier reports said that the species was a Pilot whale.
Sabin said that this was the first sighting of this species in the Thames since records began in 1913.
Peter Evans of the Sea Watch Foundation told Reuters that the whale may have gone up the Thames to chase fish or because it was sick or disorientated.
"Sighting of things like Porpoises in the estuary have become more frequent in the past five years - indicating that fish have become more abundant which in turn shows how much cleaner the river is than it used to be," Evans told Reuters.
Television footage has shown the whale surfacing and expelling air near Vauxhall Bridge, further down the Thames from the previous sightings near the Houses of Commons.
Hundreds of people are reportedly lining the Thames to watch the whale, alledgedly including many staff from MI6.
RNLIThe BBC reports that the Royal National Lifeboat Institution has sent a lifeboat out to the Thames to check on the condition of the whale.
Liz Sandeman, from the whale and dolphin protection group Marine Connection accompanied the RNLI and examined the animal.
She was reported as saying: "It looks quite healthy and quite relaxed. It's breathing normally and its weight seems good."
Sandeman told the BBC that boats in the river could pose a risk to the whale.
"There's also the noise that could affect it. The Thames is extremely busy. The last thing we want to do is stress the animal out.
"Some people think it has losts its way or is not feeding well, but it's very hard to say why it is here."
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