The mammal's been spotted twice in as many says.

A rare beluga whale has spotted in the River Thames in London for a second time in as many says.

Ecologist Dave Andrews first shared video of the mammal on social media yesterday.

Just after 9.30am today, Irish Sky News reporter Enda Brady spotted the whale again - writing on Twitter that it had "just surfaced on the Gravesend side of the estuary".

It appears to have moved a few miles further west since yesterday.

It's not clear why the whale, usually found in the Arctic, came to be in the River Thames but one theory is that it followed a shoal of fish while seeking food.

Experts have said the whale may be lost and in danger and rescue teams are on standby.