Published: 10:37, 07 October 2019
| Updated: 08:15, 08 October 2019
A humpback whale was spotted coming up for air last night by curious onlookers along the Thames Estuary.
The rare species was spotted in the river just after midnight, between Crayford Ness and the Queen Elizabeth II Bridge, Dartford.
PC Dempster, a member of the Metropolitan Police Marine Policing Unit, witnessed the sea creature, which in adult form can weigh up to 30 metric tons, during an overnight patrol.
He said: "It was spectacular! Was gobsmacked it was so big. Would estimate about 15 metres."
David Callahan, who spotted the whale further along near Rainham, Essex, said: "It looked to be about eight metres long. Remarkably undisturbed by container ships going up and down. Just kept on diving. It's hard to imagine much food for it there."
The British Divers' Marine Life Rescue service confirmed the sighting of the giant mammal which has been nicknamed 'Hessy' by some users on Twitter.
A member of the team said: "We observed the humpback in the estuary for just over three hours today, the whale was diving and surfacing at approximately five to six minute intervals, slowly moving down river with the outgoing tide."
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The rescue service said it will continue to monitor the animal's movements and is asking volunteers and member of the public to help with this.
Marine charity, Whale and Dolphin Conservation, has waded into the debate as to why the creature can be seen bobbing along the Thames.
It believes the young humpback probably followed prey into the area and has now managed to get off-course.
A statement from the organisation read: "Food (and reproduction to a lesser extent) is the driver of all cetacean movements. Hopefully this is not indicative of a lack of available prey in usual habitat and is in fact just a young inexperienced whale whom has become a bit distracted and ended up where he or she is not meant to be."
The whale is reported to be heading upstream where hopefully it will reach the Channel and then into deeper and more productive waters.
The RSPCA said at the time there were "no major concerns" for the creature.
More by this authorSean Delaney